It's getting hard to know what else Silvio Berlusconi, the Italian prime minister, has to do to get evicted from power. In most countries, just one of the dozens of scandals he has been involved in would be enough to finish him off politically. Each time a new scandal explodes, more sordid and incredible than the last, you think he can't possibly ride this one out. He can't possibly, you hopefully imagine, survive a court verdict that says he was bribing a lawyer to give false testimony or just shrug off the mountain of evidence that he regularly organises orgies with paid escorts at his private, and official, residences. And yet, there he is, still in power, still the leader of one of Europe's most cultured and important countries. After all these years, it still beggars belief.

I'm sure you've heard it all before, but it's worth remembering how many scandals he has so far survived. There have been the endless court cases for corruption which have led to a confusing series of convictions and absolutions. For anyone who has followed the story of the acquisition of the Mondadori publishing giant, or the David Mills case, there's more than enough smoke to suspect one hell of a lot of fire. Berlusconi was found guilty of perjury when he denied that he was a member of a sinister, far-right masonic lodge, P2, that was dissatisfied with the drift of democratic politics.

There have been repeated whispers about an incredible proximity to the mafia: back in the 1970s he employed as a stable hand a man called Vittorio Mangano, a mafioso convicted for murder, drug trafficking and extortion. Berlusconi has never explained what he, a Milanese businessman, was doing employing such a gentleman. Nor has he ever adequately answered one of the greatest mysteries in his astonishing career: who put up the huge sums of capital to fund the construction of his housing estates in the Milanese suburbs almost 40 years ago? There has long been suspicion that he was being funded through a bank, the Banca Rasini, where his father worked and where various Sicilian godfathers put their "savings". Indeed, one of his closest allies, Marcello Dell'Utri, was recently sentenced to seven years for collusion with the mafia. Various super-grasses have emerged in recent years to say that Cosa Nostra saw Forza Italia, Berlusconi's political party, as the right Trojan horse with which to enter power. The fact that Berlusconi won 100% of the directly elected seats in Sicily in 2001 says everything about which horse Cosa Nostra has decided to crawl inside.

And then, of course, there are the prostitutes. The Italians are far less puritan than us about such things, and sex scandals as such are rare. Berlusconi's active sex life has become a political issue not because he's getting laid a lot but because he's said to have told so many lies about what's going on that he makes Walter Mitty appear like a slave to the truth. When he was photographed at Noemi Letizia's 18th birthday people began to ask how on earth a teenager got to hang out with the prime minister and why she called him "Daddy". Berlusconi's reply was that her real dad was an old friend because he used to be the chauffeur of Bettino Craxi, Berlusconi's political protector in the 1980s and a man who fled to exile in Tunisia to avoid corruption charges. The chauffeur story, of course, was complete bull. So how did he know her? No one knows.

He seems to have been offering businessmen such as Giampaolo Tarantini from Bari breakthroughs in their business deals in return for a supply of women. He is said to have been interfering with justice by springing a 17-year-old Moroccan call-girl named Karima El-Mahroug – stage name Ruby Rubacuore, or "Ruby Heart-robber" – from jail by saying she was Egyptian leader Hosni Mubarak's granddaughter. Ruby has described orgiastic sex games called Bunga Bunga, a word which will never now leave the Italian lexicon. Berlusconi's soon-to-be ex-wife has said he frequents minors and needs help. The divorce between Veronica Lario and Berlusconi is due to be finalised soon, further removing him from the sound advice or wise oversight of a spouse.

In the words of one of the opposition leaders, "the problem now isn't judicial or political, it's psychiatric." But even all those stories paled into insignificance last week as new allegations emerged about teenage girls smoking dope in Sardinia that had been flown in on Berlusconi's private jet. One of those interviewed by magistrates has claimed that he gave her 10,000 euros in an envelope after a sexual encounter and that he also phoned her mother to ask what he could do for her. Nice touch.

Until recently the sex stories have seemed barely to dent Berlusconi's reputation. Many Italians envy or admire his success with women – if that's what it is if you pay 10 grand a time. Many of the electorate seem to like the fact that their leader is reliably red-blooded and doesn't lie about it. It's telling that it was one of his own magazines that splashed the first "Berlusconi and his harem" story three years ago: they seemed to know that having teenage girls on his lap would only help his poll ratings. But even that blase attitude seems to have changed. It has changed partly because it seems likely that he is repeatedly compromising security; and partly because his eye for women appears to determine who gets a job, who gets a contract, even who gets into politics (like the former show-girl Nicole Minetti). And, relaxed as the Italian electorate is regarding sex, they know hypocrisy when they smell it. Last week, just as the latest revelations were emerging, Berlusconi's government announced that street prostitution would be made illegal. It was a bit like an alcoholic headmaster telling his schoolchildren that they couldn't drink Coke.

But most of all, attitudes have changed because Italians admire style and charm and panache, especially when it comes to seduction, and Berlusconi has repeatedly come across as nothing more than a feudal groper and a doddery old bigot. Visiting Aquila after the earthquake 18 months ago he turned to a city councillor and said: "Can I fondle you?" He gives the impression he really does believe in droit de seigneur, the medieval ritual that the overlord should have first pickings of his kingdom's virgins. He said as much to one of his female parliamentarians. Berlusconi's defence for his weakness for female flesh ("better a passion for beautiful girls than being gay") was also seen as simply stupid, a crass, offensive comment that would in itself have created a scandal in any normal country.

But as much as everything Berlusconi has done, the crisis has also come to a head for what he hasn't done. The residents of Aquila are still living among the ruins of their houses 18 months after the terrible earthquake. For all his promises, Berlusconi's government has been almost completely absent. (It's telling that on the day of the earthquake constructors were recorded by magistrates chuckling at the amount of money they could make out of the tragedy; and that the head of the Civil Protection, the man responsible for the reconstruction, is said to have received late-night "goings over" from a Brazilian masseuse laid on by those same constructors.)

Just this week, a central part of Pompeii fell to the ground, another victim of government neglect and incompetence. It seems that parts of Italy are literally in ruins while the only thing the great leader cares about is getting his end away. He has turned his country into a complete joke: even British comedy shows such as Harry and Paul or Bremner, Bird and Fortune have regular slots spoofing him. There are so many smoking guns surrounding the man that it often looks like a war-zone. How on earth is he still in power and how on earth will the Italians ever get rid of him?

The most obvious reply, and still the most convincing, is the simple fact that he and his family own vast swaths of the Italian media: three national TV channels, a huge publishing firm, a major newspaper and dozens of magazines. The true parliament, the real focus of national debate, is the TV chat show and Berlusconi, of course, owns most of the studios. That concentration of media power in his hands means that any political fight appears like a contest between a nuclear power and a kid with a dagger. Whenever anyone dares criticise Berlusconi the dogs of war are unleashed and a smear campaign is mounted. Gianfranco Fini, long thought of as Berlusconi's dauphin, was the chosen victim this summer. As Fini tried to distance himself from the political car crash of Berlusconi's government, he was accused of financial impropriety in his property dealings in Monaco. Emma Marcegaglia, the young head of Confindustria (Italy's equivalent of the CBI) and vocal critic of Berlusconi, has faced similar smears. I've been a victim myself. Years ago, when I published a book that was teeth-grittingly angry about everything Berlusconi was doing to Italy, a long article appeared in one of his magazines denouncing me as the "English Pinocchio"; his scary minister of communications accused my writing of being a mixture of "marxism and bigotry". For as long as Berlusconi holds such media power, no one really dares to wield the knife. To do so would be, paradoxically, not political ambition but political suicide.

It's telling that the most credible threats to him come from his own camp, because the centre-left opposition is notoriously divided and weak. In the 12 years that I've been reporting on Italian politics the centre-left has changed leader and portfolios so many times that it feels like they're just frantically playing musical chairs. The leaders in that time have been – off the top of my head – Prodi, D'Alema, Amato, Rutelli, Fassino, Prodi again, Veltroni and now Bersani. And while many people loathe Berlusconi, many more, I'm afraid, find the centre-left parties fairly pathetic. The Northern League has been incredibly successful at mopping up the working-class vote in huge swaths of the north that used to be part of the reliable, leftwing rump.

And it has become very clear that, if no one will ever wield the knife politically, nor will Berlusconi ever fall on his sword. For all his faults, he's a fighter, a dogged, determined, never-say-die sort. When he spent five years in opposition between 1996 and 2001 he spoke of it in biblical terms as his "time in the desert". But such is his messiah complex that he never doubted he would enjoy a political resurrection. The only time I've ever had a grudging admiration for him was when, recently, a miniature statue of Milan cathedral was thrown at him, breaking his teeth and causing much blood. As his security men tried to bundle him away, he stood up on the car and shouted defiantly at his assailant. Here was a man in his 70s who had been pretty severely bloodied, who might rightly have assumed that his life was under threat, and he had the courage to face down his attacker. He is the same in politics. Any attack will immediately be met with counter-attack. He will never, ever give up.

In most countries, the usual mechanism to remove that sort of leader is by appealing to the national interest. In that way a politician's exit can give them some dignity, and they can relish the sense that they are making a great sacrifice in the interests of their beloved country. But although Berlusconi really does believe he is some sort of saviour, he's not the sort of saviour who believes in self-sacrifice. And nor, moreover, does he believe in the national interest. Barely anything that has happened under his government suggests he has any notion of the interests of Italy. He has spent almost two decades subjugating the country's interests to his own: trying to ruin RAI, the national state broadcaster and rival to his own media empire, Mediaset; decriminalising false accounting; decreasing the statute of limitations so that crimes pass their sentence-by date incredibly quickly. Every political decision, it seems, serves Silvio, not the peninsula as a whole. The tragic genius of Berlusconi is that he appears to have convinced millions that his destiny is their destiny: everyone who is scared of becoming a victim of judicial persecution, who feels overtaxed, who fears that foreigners are condescendingly critical of the Italian way of life is subtly persuaded that getting rid of Silvio would leave them vulnerable and isolated.

And yet many of his fanatical admirers now admit that the man is a liability. Every time he steps on to the world stage Italians hold their breath and wait for him to humiliate himself and their country: in recent years he has called Obama "tanned", he has been told to pipe down by the Queen, he has kept Nato leaders waiting while he turned his back on them and yakked on his mobile phone and he has made a pistol gesture at an awkward journalist. And yet the country seems unable to throw him off: Fini seems to lack the cojones to vote against him in a confidence motion and the opposition can't do it by themselves. Part of the problem is that anyone seen as responsible for forcing elections, and risking parliamentary approval of the 2011 budget at a time of profound economic crisis, will be punished at the ballot box. Parliament is paralysed. The government lost three votes in one day last week. Yesterday, a week after demanding Berlusconi's resignation, Fini's Future and Liberty party formally left the coalition. But the government is still there, like a battered boxer who has no trainer to throw in the towel.

The size of the problem was illustrated to me recently in conversation with a gentle lawyer from Rome. Conversation had turned, as it does with monotonous regularity, to Berlusconi, and the lawyer confided that he felt assassination was the only way the country would ever liberate itself of the man. He's normally such a pacifist that I assumed he was joking, but he was serious. He couldn't see any other way in which the country could get rid of its prime minister. Now I dislike Berlusconi as much as anyone, but I would far rather have him in power than have a return to the bloodshed of the "years of lead" in the 1970s. And yet when a law-abiding, middle-class, Catholic lawyer starts talking quite seriously about armed insurrection you know something is terribly wrong in the country, that it has reached a very dangerous political cul-de-sac.

And so the country finds itself in a stalemate, unable to continue with Berlusconi but unable to replace him. Ever since he came to power in 1994 he has been, in the words of the late Indro Montanelli, "the boulder that paralyses Italian politics". There is no political discussion without mention of the man. Everything revolves around him. You never go out to dinner without his name coming up. Every election since 1994 has basically been a referendum on him, with the current score – he likes his football analogies – 3-2 in his favour. Getting rid of him isn't simply a question of an election or a political coup. He has lost before and has bounced back. The only way to liberate Italian politics from his immense and deleterious influence would be either for him to pass away, or for the country to undergo a thorough, programmatic deBerlusconification, an attempt to return to reality after 20 years of his televisual brainwashing. The first, I'm afraid, is more likely than the second, but it still seems a very long way off.