Inside Ethiopia’s flagship stadium, the bleachers are painted the green, yellow and red of the flag. The country’s best athletes have converged in Addis Ababa for the national championships while the great and good of Ethiopian sport gather trackside in matching beige suits and white baseball caps.

Haile Gebrselassie is among them, handing out medals in his capacity as the president of the Ethiopian Athletics Federation. He receives a louder cheer than anyone when introduced by the stadium announcer. Two Olympic and four world 10,000m titles mark him out as one of the greatest distance runners of all time and the most famous man in Ethiopia, where athletics is the national sport. His reputation has helped build an enviable property and business portfolio, making him a wealthy man.

At one end of the stadium a billboard pictures other distance running greats Kenenisa Bekele, Tirunesh Dibaba and Almaz Ayana, whose extraordinary 10,000m world record at the Rio Olympics last summer was greeted with disbelief in some quarters. Beneath them, in bold writing, is the statement: “It is possible to be the best without doping.”

However a joint investigation by the Guardian, the German broadcaster ARD and Holland Media Combination suggests that may not be true in every case. It shows how easy it is to obtain doping products in the country and there emerges a prevailing sense of disorganisation at the Ethiopian anti-doping agency, which is charged with testing athletes. A hugely successful Ethiopian athlete is also caught on undercover film, seeking a new doping programme and admitting to having taken performance-enhancing drugs before claiming one of her biggest titles.

The findings may raise concern for British Athletics, which holds annual high-altitude training camps in Ethiopia for top athletes, including Mo Farah, who is attempting to do the distance double for a third time at the world championships in London, which begin on Friday.

Outside the national stadium, two girls sell cobs of corn and coffee beans from colourful mats on the ground. But during the week of the Ethiopian championships, the blood-boosting drug EPO could be bought freely from a pharmacy just over the road. It is a popular drug, particularly among athletes and cyclists looking to gain an illegal edge by enhancing their endurance levels.

A sign for the Gishen pharmacy is broken at one edge but potted plants decorate the doorway and it is clean inside. First, a reporter from the Guardian asks for something to treat anaemia, suggesting EPO as a possible medicine. A female pharmacist disappears into a back room briefly and delves into a fridge, returning with a cardboard box filled with dozens of phials of EPO stacked one on top of the other. She asks nonchalantly how many are required and three were bought for 810 Ethiopian birr (around £26) in cash.

The same reporter returned a second time only 13 minutes later, buying a further two phials of EPO, a toothbrush and a tube of mosquito repellent from a different pharmacist. A different reporter then entered the pharmacy and bought four phials of EPO from a third person. A male pharmacist admitted he knew of the performance-enhancing benefits of EPO and had sold it to athletes. “Sometimes, yes,” he giggled.

In the space of 26 minutes, nine phials of EPO were purchased at a cost of 2,430 birr (£79). A sticker on the reverse of the glass container states they should be dispensed on the prescription of a physician only. But no questions were asked. No prescriptions were sought.

The nine vials of EPO which were bought for £79. Photograph: Martha Kelner

The director general of the Ethiopian anti-doping agency, Mekonnen Yidersal, promised to investigate. He said: “If somebody is involved with this illegal practice, he or she will be punishable as per the World Anti-Doping Code and other relevant anti-doping laws of Ethiopia.”

The fact EPO is so easily purchased close to the national stadium is a strong contradiction of the suggestion Ethiopia is getting tough on drugs cheats. The country has introduced deterrents of prison sentences of between three to five years for anyone found to be doping. Only this year, Gebrselassie was proudly announcing the first prison sentence had been issued, with Girmay Birahun, a little-known 22-year-old marathon runner, sent to jail for doping.

The IAAF, athletics’ world governing body, has been working with the country’s anti-doping agency and suggestions behind the scenes are that it has been impressed by a commitment to anti-doping education, with one official saying it outstripped many western nations. But when asked to provide testing figures from the national championships, a very confused picture emerged.

The championships took place from 16 to 21 May but the first set of figures supplied were for 21 to 26 May and suggested 111 in-competition urine tests were conducted and 15 pre-event blood passport tests. However a total at the bottom suggested 18 blood tests and 83 urine tests had been carried out. When the figures arrived for the correct dates, they had been altered. The anti-doping room is in the bowels of the stadium, signposted by an A4 sheet of paper taped to the door but it remained locked for several hours during one day of the championships when 16 tests were said to have been conducted.

In a statement, the Ethiopian anti-doping agency said: “Regarding to the testing figures conducted on the 46th Ethiopian Athletics Championship, there was a mistake occurred on the table when we wrote in the tab.

“The final day was Saturday and Sunday. Therefore some of our staff, including me, were in the stadium to facilitate the outreaching programme and sample collection process. On the other hand, since the day was the weekend, some of our staff were out of office.”

For years, it has been Ethiopia’s east African neighbour Kenya in the spotlight for doping offences. Last year another documentary by ARD contained allegations that doping was rife at a high-altitude training camp in Iten including a doctor filmed on a hidden camera claiming he had supplied “more than 50” athletes, including three British runners, with doping products.

Even before that documentary, there was a shift by British athletes – including Farah – from Kenya to Ethiopia. They mostly train in Sululta, a village 2,500m above sea level and about 10 miles north of the capital up a treacherous, windy road, wide enough for only one vehicle in parts. If you reach Sululta early enough in the morning there is a vista over sprawling Addis Ababa before the smog sets in, enveloping a city of four million people. The attractions for athletes, aside from the altitude, are miles of dirt trails and solitude in a place where entertainment options are limited to a cup of coffee at a roadside cafe.

There is one athletics track, with a man selling bamboo from a wheelbarrow at the entrance. On the track the Djiboutian athlete Ayanleh Souleiman, a former world indoor champion over 1,000m, jogs with a training partner. He and Ethiopia’s highest-profile athlete, the 1500m world record holder Genzebe Dibaba, regularly train in Sululta and until last year were coached by Jama Aden. The Somalia-born Aden was also used by British Athletics as an “unofficial facilitator” for Farah at a training camp in Ethiopia in 2015. There is no suggestion of any wrongdoing by the Briton, who has never failed a drugs test.

A lot of people have moved from Kenya because it is more in the spotlight, to Ethiopia because they are less likely to get caught. Ethiopian runners, most of them, don’t have money to buy their own doping products so I think it is agents and managers getting them An Ethiopian-based athlete

Aden was arrested last year after EPO and other medicine was found in his hotel room in Spain, where he was at a training camp with athletes including Dibaba, a favourite for gold in London. There is a warrant for Aden’s arrest in Ethiopia but the Guardian understands he returned to Addis Ababa for 48 hours earlier this year before fleeing. He was also spotted at the Doha Diamond League in Qatar, where he used to be a national team coach. Following Aden’s arrest Dibaba said their relationship was based only around training and that she was “neat and crystal clean”.

Last month Spanish prosecutors said Aden had been indicted on public health charges. The Guardian understands that the Spanish police also have a lot of evidence from mobile phones and laptops seized in the raid last year, including text messages and emails that suggest drug trafficking as well as administering banned substances to athletes.

The IAAF anti-doping department is understood to be confident this additional evidence will be enough to pursue rule violation charges once the criminal case is concluded.

Back in Addis Ababa there is more evidence Ethiopia’s phenomenal track and field success is not purely down to the popularity of the sport and a genetic edge African-born runners possess. A high-profile female athlete is caught on a hidden camera asking another athlete about sourcing a new “doping programme”. She talks casually about her running schedule, admitting to having taken Eprex, a brand name for EPO, before one of her biggest victories, in Europe several years ago.

After much discussion she settles on a 45-day programme, taking EPO and human growth hormone on alternating days. It is agreed she will tell the fictitious doctor who has devised the programme about her progress and she will stop taking both substances a week before she is due to compete in order to evade the testers.

Many Ethiopian coaches blame the prevalence of doping in the country on increasing numbers of foreign coaches and agents, particularly from eastern Europe. Yirefu Birhanu, an Ethiopian Olympic team coach who led Feyisa Lilesa to silver in the marathon in Rio, believes the relative poverty in Ethiopia and lack of education can mean athletes are tricked into taking drugs.

“I had two athletes test positive,” he says. “When I asked them they said they were told it was not a banned substance, that it was vitamins and many famous athletes are using this. But the athletes have already killed their life because it was a banned substance.

“There are a lot of managers,” he adds. “Some are doing their business from their heart. Some are doing it for money only, they care when the athletes are participating in races, after that they throw them away.

“I am advising to those managers, they must show all the information to their athletes. Because they are human beings, they are not a cow or something like this, they have their own right to know what they are doing.”

Another athlete who has trained in Ethiopia since 2003 has noticed the availability of drugs increase with an influx of coaches from eastern Europe. “I believe it is foreign coaches bringing doping into Ethiopia. I think a lot of people have moved from Kenya, because it is more in the spotlight, to Ethiopia, because they are less likely to get caught. But I think it is more of an individual issue than a state-run thing. Ethiopian runners, most of them, don’t have money to buy their own doping products so I think it is agents and managers getting them.”

British Athletics declined to comment but said it was satisfied all athletes on training camps in the country were subject to rigorous anti-doping procedures. The UK Anti-Doping chief executive, Nicole Sapstead, said: “Under the World Anti-Doping Code, UK Anti-Doping has the jurisdiction to test any athlete from the UK, anywhere in the world. We do test athletes internationally, including Ethiopia and from April 2016 to March 2017, we conducted 558 tests across 17 different sports in 22 countries.

“Sadly, it is not uncommon for substances such as EPO to be available to purchase in a number of countries, and we are concerned about the increase in the number of people buying such substances over the internet. We would appeal to anyone with information about these substances being bought or used to contact us in confidence via reportdoping.com.”