When Tom Welch greets me in the foyer of Salt Lake City's Marriott hotel, he is dressed in black from head to toe. His face is podgy and there are worry lines gouged into his thick cheeks but his handshake has a firmness of intent. He sits with his back to the wall, periodically nodding to the hotel staff who appear intrigued. You can almost hear them whispering: 'Isn't that the guy who...' For two years he has evaded the world's press, silent on the issue that has made him a pariah, but now he has agreed to give OSM his first in-depth interview. It is soon clear he is dying to tell his side of the story.

In five weeks, Salt Lake City will host the XIXth Winter Olympic Games. Welch was the chairman of the Utah city's Olympic bid team. When they finally won the race for the 2002 Games, Welch had spent more than $10 million, lavishing gifts on members of the International Olympic Committee to win precious votes. The gargantuan scale of corruption might never have become public had Welch, a Mormon bishop, not had a stand-up public row with his wife over presents he had bought for his mistress. The police were called and, in moral-minded Utah, this scandal forced him out of his job and ultimately led to the detailed revelation of the avarice of the IOC and its members. At one time the tales of sleaze became so extraordinary, so damning, that they seemed to place a question mark over the Games taking place at all. However, a one-month investigation by the IOC resulted in a handful expulsions and reprimands and the Olympic movement pronounced itself cleansed. All the same, a 22-month inquiry by the Salt Lake Organising Committee's Board of Ethics, which reported its findings a month, later makes grim reading.

Welch is unrepentant. 'I didn't believe what I was doing was unethical. My community had spent a lot of money on this and it would have been unethical of me not to have done everything in my power to win.' That meant 'playing the game' as every other bidding city played it. But with Salt Lake the game spiralled out of control.

The handwritten memo arrived on 10 October 1994, and began 'Dear Dave'. It spilled out of a fax machine on the top floor of the high-rise offices looking down on South State Street, Salt Lake City. David Johnson read it and passed it on to Tom Welch. Yet another member of the IOC was asking for money. This time it was General Zein Gadir, the Sudanese representative who had entertained them with amusing stories while making liberal use of their credit card with his drinks bill during his last visit to the city.

The memo was from a middle man, the Kuwait-based director of the Olympic Council of Asia, Muttaleb Ahmad, to whom Johnson and Welch had paid a lobbying fee of nearly £50,000 to help secure the support of the Middle Eastern and North African IOC members. 'Finally got through to Gadir,' Muttaleb wrote in his broken English. 'On a personal level. He has a daughter in UK. Help may be extended. He expect $1,000 only a month to Zema Gadir.'

To the outsider, unfamiliar with the Machiavellian world of Olympic politics, Gadir may have seemed a surprising choice as his country's IOC representative. After all, his sporting connections were tenuous, to say the least. He had founded Sudan's parachute regiment and spent years as a political prisoner before rising through the ranks of the brutal military junta to become a Minister for Youth, among other things. (The sporting connection came from a stint in the national military football team many years ago.)

But a lifelong interest in, let alone talent for, sport is a hardly a prerequisite for IOC membership. The 126 IOC members come from all backgrounds, including arms dealers, former spies, politicians, lawyers and royals - though there are a few plain old sports administrators. Their power is enormous because there are so few of them and they hold the destination of the Games in their hands. Each of the IOC members casts a single vote when deciding on the venue for the Games. The vote is made in person at an IOC meeting and is secret; at no time are the votes attributed to a specific person and there is no procedure to make the individual votes public. Given that such a choice can be worth millions, perhaps billions, of pounds and that up to a dozen cities will be competing for either the Summer or Winter Olympics at any one time, theirs is surely the most potentially corruptible role in world sport.

Like many of his fellow IOC members, Gadir owed his position on the committee to its president, Juan Antonio Samaranch, who effectively controlled nominations. Once a member, it wasn't long before Gadir started taking advantage of his position. The team from one bidding city, Stockholm, for instance, found his behaviour so detestable that they wrote to the IOC complaining that he was constantly drunk during a visit to the city and behaved offensively to fellow guests. In Berlin, his hotel room service bill alone cost more than £1,000.

But despite Gadir's reputation Welch and Johnson didn't think twice about the memo. After all, they were already committed to spending $17,000 in college fees for another of his eight children. That was because Gadir was important. There were seven months to go before he and his fellow IOC members were due to meet in Budapest to decide which city would host the 2002 Winter Games. The African vote was crucial, especially as the Salt Lake team were assuming the Europeans would, as always, vote against an American city.

They immediately began wiring the cash to Zema's bank account in London. The last of their seven payments was made only days before the IOC met on 16 June 1995 to vote on the venue for the Winter Olympics.

It was only much later that the scale of Gadir's corruption was revealed. Perhaps if Welch and Johnson had taken a closer look at his full name they would have rumbled him: Zein El Abdin Mohamed Ahmed. Zema was a pseudonym - a rough abbreviation of his forenames. Zema did not exist. The money was meant for Gadir.

Gadir's tale is but one example of many which show that, for all its idealism, the modern Olympic movement has as much to do with money and commerce as it does with sporting excellence. If they didn't realise this already, the truth dawned on Salt Lake City's team when, in 1986, they put together a bid for the 1998 Winter Games. The bid was entrusted to Welch, a millionaire who had made his money from property and as corporate lawyer for his father-in-law's grocery store chain. Welch describes himself as 'not the brightest light on the block' but his new role threw him together with a smart and savvy young blue-eyed community sports director called David Johnson. They were to become firm friends. The relationship was cemented by marriage, when Johnson married a young television reporter in Welch's congregation at the Latter Day Saints nineteenth ward.

Welch and Johnson threw themselves into the campaign with zeal, and after three years they had wrested the crucial US bid city status from Anchorage. At the same time they were initiated into the extraordinary world of the Olympic family. As recorded by the Salt Lake Board of Ethics report, Salt Lake was outclassed by the Nagano bid which they said was 'more sophisticated and extravagant' and pampered the IOC membership, with a greeting that included Geisha girls. Japanese companies arranged for $15m in donations to be paid to Samaranch's pet project, the Olympic Museum in Lausanne.

When they arrived in Birmingham, England, in June 1991 for the final vote, Salt Lake gave each IOC member a disposable camera as part of a welcome package but Nagano outbid them again, handing out video cameras. The Mormons almost got knocked out in the first round of voting but recovered to get within four votes of Nagano. For the Salt Lake City team, this failure was to prove a watershed.

They would bid again, for the 2002 Games, and this time they would do it properly. Four months after losing out to Nagano, Welch's mission statement made everything crystal clear. They would 'establish and maintain long-term, vote-influencing relationships with IOC members'. This would involve extensive use of the corporate credit card and would seriously test the integrity - or should that be greed? - of the men and women on the IOC. (The Salt Lake Board of Ethics report later exonerated the Salt Lake trustees, absolving them of any knowledge of payments to IOC members or their families, but criticising their failure to control Welch and Johnson.) Welch and Johnson were eager to please Samaranch. The former official in Franco's fascist regime ran the IOC as a private fiefdom wielding tremendous influence over the membership who were, in effect, his appointees. His regal first-class jaunts may have been seen by some IOC members as an indication of the lifestyle they could expect. But Samaranch did not receive gifts or money in breach of the IOC's rules.

Welch and Johnson soon got the hang of things. A key figure on the IOC executive committee, had just bought a new house. He went shopping with the Salt Lake organisers for wallpaper, doorknobs and other household items at their expense. A note in the accounts shows that the doorknobs alone cost $673 and that at least $30,000 was spent on similar shopping trips for IOC officials and their families. The list of items bought included lawn equipment, bathroom fixtures, hardware and even a refrigerator.

But it wasn't just gifts. Many IOC members simply asked for cash - some suggesting it would be used for their athletes at home. Welch wired a total of $29,450 to the the personal account of Kenya's Charles Mukora, after a request for 'personal financial assistance'. Another $20,000 was wired to Chile's Sergio Santander-Fantini, who said he used it for his political campaign. (He later told the IOC he thought it was a personal gift to his political campaign from Welch and his wife, otherwise he would not have accepted it.) Cameroon's Professor Rene Essomba was given four separate payments by cheque and wire totalling $15,000.

However, their rewards were dwarfed by those received by Congo's Jean-Claude Ganga, who became known as 'the human vacuum cleaner' because of his ability to hoover up Salt Lake's generosity (see panel). Chastened by past failures, Salt Lake had a straightforward policy to the requests of IOC members, no matter how outlandish. They would always say yes. Ganga proved the exception to the rule, but not before they had spent a quarter of a million dollars on him.

But it wasn't just gifts and cash. In January 1992, Salt Lake introduced a 'Scholarship Program' to 'provide opportunities for National Olympic Committees to nominate outstanding individuals to attend universities and colleges in Utah'. In truth, while some funds were used for this purpose, the really outstanding individuals to benefit were the sons, daughters and friends of IOC members. Sibo Sibandze, whose father David was the member for Swaziland, received $111,389 for his education at the University of Utah. Nancy Arroyo, the daughter of the Ecuadorian IOC member, was given $23,000 in living expenses even though she didn't enrol on a course. A supposed relative of the Algerian member, Mohamed Zerguini, was paid $14,500 to live in Atlanta and Essomba (again), managed to get $108,350 towards his daughter's rent, expenses and fees while studying at Washington's American University.

When John Kim, the son of the influential Korean IOC member Kim Un-Yong, lost his job in New York, Welch was there to help. He found John a job with a local telecommunications firm and struck a deal whereby the Salt Lake bid committee would pay the young man's salary, minus any commission he earned. John stayed in New York and didn't earn much commission. Salt Lake ended up paying his employer between $75,000 and $100,000. John's father Kim Un-Yong told the Salt Lake Board of Ethics that he was 'unaware of any relationship between the [firm] and the Salt Lake City bid committee' and that 'John Kim never knowingly received any sums from anyone associated with the ...bid committee.'

On one occasion Welch wired more than £20,000 of his own money to the wife of the IOC member from Western Somoa, Seiuli Paul Wallwork, who had written asking for a loan. Other members of the IOC were given free health and dental care. Bjarne Haggman, the husband of Finnish IOC member Pirjo Haggman, received a total of $33,750 from the Salt Lake bid committee for producing a report on forestry for a Utah engineering firm. All requests for assistance from Salt Lake came from Bjarne directly and the ethics committee report found no direct evidence of Pirjo's involvement.

Allegations also surfaced that some members enjoyed the services of escort girls. The owners of Salt Lake's Snow White Escorts were later to claim that their girl had done her bit for the bid effort, stripping naked in the hotel rooms of two IOC members.

By June 1995, when the IOC met in Budapest, Welch and Johnson had done their jobs brilliantly, if expensively. The lessons of the previous campaign had been learnt, more than $10m had been spent, and the election was in the bag. Salt Lake won by a landslide - 54 votes to the 14 of its nearest competitors Ostersund and Sion. God had been on the side of the Mormons.

Salt Lake's massive sweetener campaign would almost certainly have remained secret had it not been for one person's sexual weakness amid this sea of financial corruption: Tom Welch's marriage was in trouble. First there had been a fling with the Canadian IOC member Anne Letheren during the bid. It was frowned upon by his colleagues, but didn't present a conflict of interest because she was always going to vote for Quebec. Then Welch met Nancy Fay Money, a four-times divorced waitress, at Lumpys Social Club in Salt Lake and she became his mistress.

The situation might have been containable until a farcical scene was played out at Welch's home in Sherwood Circle, an affluent Salt Lake suburb on the afternoon of 9 July, 1997. Welch was sitting on the boot of his BMW as his wife Alma, dressed in just a towel, frantically tried to prise it open. Inside the the boot were presents for Nancy: something slinky from Victoria's Secrets lingerie store and some perfume with an attached note saying: 'Please don't use this with anyone else but me.' Alma was hysterical. She had been in the shower but had crept downstairs to see what Welch was up to. She had long suspected her husband was having an affair and the pink frippery she glimpsed in the boot appeared to confirm it. She managed to seize one of the notes to his mistress.

Tom slammed the boot shut and a struggle took place. The police were called. The Mormon city fathers who had backed Welch were particularly sensitive on the question of women, so when the news broke that Welch was being investigated by police for assaulting his wife there was a power struggle on the organising committee and Welch was forced to resign.

Welch was no longer in a position to keep a lid on things. He was replaced by Frank Joklik, a former mine boss with a quick temper. Within months Joklik's autocratic style was antagonising members of the committee's staff, with the result that one of them sent a letter to an investigative reporter at a local TV station that contained details of a scholarship arrangement with an IOC member.

Still the story did not excite much interest, until Howard Berkes, a reporter for Salt Lake's National Public Radio, phoned Marc Hodler, a senior IOC member and probably the committee's leading anti-corruption campaigner. 'This is the information we need,' said Hodler, promising that it would be used to identify and punish corrupt members. The Salt Lake bid committee was forced to accept that at least six IOC members' relatives had received 'humanitarian aid' through the scholarship programme totalling half a million dollars, although they denied bribery. It was the spark the story needed. Soon journalists everywhere were rooting out Olympic corruption stories in their own backyard. Reports of IOC excesses came from Stockholm, Berlin, Atlanta and Sydney. Hodler, a former Swiss skiing champion now in his sixties, was giving interviews to everyone. 'There is a list of IOC members who can be bought,' Hodler told one reporter. But the IOC report concluded that everything Hodler knew was simply hearsay, 'the truth of which he was unable to verify personally'.

The pressure on Salt Lake was enormous. Joklik, too, was forced to resign in January 1999. He denied knowledge of the cash-for-votes scheme but he had been a trustee during the bid years and was therefore tainted. The ethics committee report concluded that the trustees should have been more vigorous in their supervision. Jolik demanded that David Johnson go with him. Welch had already gone. As the world's press bombarded Welch and Johnson for comments, the duo remained silent.

The organising committee, however, opened up its files to its own ethics committee which began to scrutinise the actions of its employees. The result was a damning report in February 1999 which held Welch and Johnson to blame for almost everything. However, it was regarded by some as a damage limitation exercise. It's hard to imagine who the scale of the hospitality being offered to IOC members could have gone unnoticed. A Utah police investigation into the scandal was quickly overtaken by an FBI inquiry. In the summer of 2000, Welch and Johnson were indicted by a federal grand jury on charges of bribing the IOC by paying members and their relatives a million dollars in cash, travel and perks.

Earlier, in January 1999, the IOC had produced its own report on the matter. It had been forced to act because its corporate sponsors were demanding action to clean up the tarnished image of the Games. This resulted in the expulsions of members from Mali, Ecuador, Sudan, Chile, Congo and Samoa. (The members from Finland, Swaziland and Kenya fell on their own swords.) Newspapers across Europe called the investigation a whitewash and the Africans claimed they had been made scapegoats. Later a US Olympic committee panel, headed by Senator George Mitchell, concluded that the the IOC had turned a blind eye to the corruption that was 'flourishing.' They still were. Samaranch admitted the revelations had 'seriously damaged the reputation' of the Olympic movement. He asked the members to submit further evidence of wrongdoing in other bids.

Meanwhile the criminal case against Welch and Johnson continued until last November when Utah district judge David Sam dismissed all charges. Bribing Olympic officials may be unethical, he decided, but it is not criminal. Federal prosecutors have indicated that they may appeal against the judge's decision.

Tom Welch, now aged 55, has a new girlfriend and has moved to California. There is contempt in his voice when you ask him why only six IOC members were expelled. 'It was all for show,' he says in a deep Utah drawl. 'Those were the small people. They were weak, expendable with relatively little power in the IOC structure. If what those expelled members did was wrong and everyone else on the IOC was to be judged by the same standards, then probably 80 per cent should have been kicked out.'

This calculation is based on years of witnessing the freeloading by IOC members. The 80 per cent were those that were 'imposing themselves on you, asking for things and pushing for lavish hospitality.'

There were exceptions - there is no criticism of the British members' conduct, for example - but the vast majority expected something from the bid cities they visited. 'Of course you felt used and abused,' he says. 'But you were abused by the process. The expectations of the IOC members had been created over years. They grew to accept these things as normal practice.' Turning to Gadir and his mysterious daughter, Welch is at a loss to explain the actions of a man he had grown to like. 'Should I have challenged him and asked him for verification? If you are going to offend him, the whole thing is pointless. If you complain or rock the boat, all you will do is ensure that you will lose.'

Many would regard Welch's willingness to hand over the cash as reprehensible but he is defensive on this point, claiming that he was just being practical. Utah had spent more than $60m building bobsleigh runs and ski jumps for the Games and the only way to recoup that was to bring the Olympics to Salt Lake.'

David Johnson shares the same views, though the two men's friendship didn't survive the revelations of Welch's extramarital affairs. Their wives are very close. It was a snowy Sunday evening when I met Johnson, 41, at his smart suburban home. He was outside the house clearing the drive with a ride-on snow mobile.

Inside his immaculately kept living room are four violins for his children and a grand piano which his wife plays. There is no tea or coffee in the house as strict Mormons don't indulge in caffeine. Johnson and his wife Kim are pillars of the local community.

His lawyers had hired private detectives to get the dirt on the other bid cities as part of his defence for the criminal trial. 'You have to get this in perspective,' he says. His body language is that of a man who is not used to people judging him harshly and he is clearly frustrated that he hasn't been able to put his case until now.

'There were 12 cities lobbying the same hundred people. We found that, within the window of just one year, a total of $100m was spent on those people. Salt Lake was not alone in what it did.'

His eyes were opened to the venal nature of the Olympic movement when he and Welch attended their first IOC meeting in Puerto Rico in August, 1989. 'We had never seen anything like it in our lives. There were Lear jets waiting to whisk the IOC members off to Atlanta. Toronto had reserved whole swimming pools and was giving out free drinks. Carts entered the hotel stacked with gifts for the members. A huge motorcade swept in and we thought this must be someone important. But it was just a couple of IOC members arriving from the airport.'

The Salt Lake duo had already made their first mistake by failing to book the same hotel as the IOC. They couldn't get close to the mighty IOC members. Eager to learn, they booked a short meeting with Samaranch. His message was simple: 'He told us to concentrate on the people who voted,' says Johnson. According the the Board of Ethics report, Samaranch advised them to become personally acquainted with as many IOC members as possible, for the purpose of impressing them with the strength of the Salt Lake bid.

Welch and Johnson interpretted this advice pretty crudely: they decided to spend all their considerable funds on the members themselves. According to Welch: 'We had to become these people's best friends. It was pointless talking about how good our infrastructure was. We had to build the best goodwill and the closest relationships.'

Johnson, a former Saab salesman with a charming smile, devoted six years of his life to tracking down and getting close to IOC members. He would fly to far away cities on the off-chance that one of them might be there. He was away from home for 270 days in one year, jetting from country to country and running expenses on his Mastercard of up to $40,000 a month.

'I would go to Sydney because I would have heard that an IOC member was in town. You had to go because you feared that if you weren't there, one of the other bid cities might get a whole weekend alone with one of the members.' Although teetotal, he would spend many long nights in bars or restaurants as IOC members wined and dined on his credit card. It had to be done. His all-American smile even worked on Princess Anne, one of the British IOC members, who the bid cities found frustratingly aloof. 'She returned all her gifts and was very difficult to talk to,' he says. 'But I kept showing up at so many functions just so she knew my face. It was worth it because, after the vote in Budapest, she stopped to talk to me for the first time, and said she had done the right thing.'

The votes for the host city are secret which is a great help to some of the double-dealing IOC members who are able to fool several bid cities into believing they have voted for them. It was for this reason that Welch had fallen out with the Russian, Smirnov, a vice-president of the IOC. 'He told us he voted for us in 1991 and I later found out he hadn't,' says Welch.

Pulling power of the human vacuum cleaner

Jean-Claude Ganga was so interested in Salt Lake City's bid for the Winter Olympics that he flew into Utah six times in two years. It was a chance to stay in a nice hotel away from his 10 children and do a bit of shopping with his wife Eugenie. But every time the couple went near Walmart, the staff of Salt Lake's bid committee drew in a deep breath.

Mrs Ganga needed carpets, rugs, curtains and a few things for her kitchen back home in the Republic of Congo. The price of the goods didn't matter because Jason Gull, a young bid committee executive, was always in attendance. It was Salt Lake's policy to give International Olympic Committee members and their wives anything their hearts desired, but Mrs Ganga sometimes became a bit tiresome because she loved to shop and always ran up Gull's charge card 'to the maximum'.

Ganga, a 67-year-old former ambassador to China, seemed to see milking the bid cities as a multidiscipline event: persuading them to pay for his shopping, for holidays, to help with his property deals; pay for his children's education; to pick up his medical fees (and those of his mother-in-law) not to mention wiring thousands of pounds into his personal account. Ganga's vote alone was to cost Salt Lake City well in excess $250,000.

Behind his back, the Mormons called Ganga 'the human vacuum cleaner' because he had 'an unending list of needs'. His travel expenses alone amounted to $115,000, his meals and hotels cost $14,000 and then there was his medical treatment for hepatitis and some knee replacement surgery for his mother-in-law. Salt Lake even paid for his wife's cosmetic surgery. Ganga opened an account at First Security Bank and Salt Lake started paying chunks of $10,000 into it. As the crucial vote drew closer, the cheques got bigger, rising to $30,000.

When Ganga was finally expelled by the IOC for breaking the rules on accepting lavish gifts, he claimed the money had gone to sporting projects in Africa. 'The Olympic Games are organised by individuals,' he said. 'They are not angels and saints. If you want angels and saints, go organise the Olympic Games in heaven, not on earth.'

The Swedish dossier

The dossier on IOC members compiled by the Swedish team bidding to bring the Summer Olympics to Stockholm in 2004 shows the extent to which it felt it necessary to lobby IOC members.

Mohamed Mzali, Tunisia

Background: Vice president of the IOC (1976-1980). Prime Minister of Tunisia (1980-1986)

Other info: Right now Mzali, lives in political exile in Paris. Mzali is very interested in politics and one of the main reasons that he still represents Tunisia in the IOC is that he tries to cling firmly to some kind of international part. He should always be taken out for dinner on visits to Paris.

Prince Alexander de Merode, Belgium

Background: IOC Vice-President

Other info: Considered 'difficult' and is in general rather unknown outside the Olympic world. The prince has medical problems, and that is why he doesn't smoke any longer. You should not smoke when he's around.

Louis Guirandou-N'Diaye, the Ivory Coast

Background: IOC Chief of protocol (1985-).

Other info: Known as snobbish and appreciates exclusive clothes, cigars etc. It is told that at the Committee of Evaluation's visit in Ostersund he refused to take off his crocodile skin shoes and therefore had to be carried around.

Vitaly Smirnov, Russia

Background: Sports administration.

Other info: Yeltsin's right-hand man in Russia. His NOC has a huge lack of money. Smirnov is known as a bit odd. Has good opportunities to affect the former East European countries. He is also well standing with Samaranch.

Ashwini Kumar, India

Background: Career military man.

Other info: Is said to know 'everybody'. Perhaps we should invite him to Stockholm. Kumar is head of security, but is by many judged to be too old and disorganised to have that mission.

Peter Julius Tallberg, Finland.

Background: President of the IOC Sportsmen Committee (1981-).

Other info: Tallberg has recently had a financial crash. He sold his company and went in for golf courses which didn't succeed. Known as a 'cold fish', who also is in need of support. He should 'be observed' and be selected for some kind of advisory mission.

Richard Kevan Gosper, Australia.

Background: Former top athlete. President of the IOC Press Committee (1989-).

Other info: Considered completely honest. His wife is supposed to be nice. Gosper is forceful. 'Don't BS him!'

General Zein El Abdin Abdel Gadir, Sudan.

Background:Military and politics.

Other info: Gadir was imprisoned 10 years because of political reasons. He is considered 'noicy' (sic) and 'hard'. He is easily affected by Jean-Claude Ganga. He is known for appreciating delicious food and drinking.