Even before the leak, rumours had been circulating for a while. Victoria United’s return to the top level of Cameroonian football for the first time in almost 20 years had seemed like a fairytale for the club from the seaside city of Limbe that had been playing in the South West Regional League until last year.

But more than a few eyebrows were raised in December when their president, Valentine Nkwain – a local businessman known as “Bobdidy” – ran on to the pitch in the 86th minute of Victoria’s game against Tonnerre Kalara Club and picked up the ball complaining about “bad officiating”. Despite attempts to get him to return it, Nkwain – later suspended by the Cameroon Football Federation (Fecafoot) – refused and the referee was forced to abandon the game. “This is absolutely unbelievable in the 21st century for Cameroonian football,” one fan told Sports New Africa.

It wasn’t until July that the significance of that day became clear. Victoria, known by their nickname Opopo, had been promoted two months earlier after winning the title with games to spare. But a leaked phone conversation apparently between Nkwain and Samuel Eto’o – the former Barcelona striker who has been president of Fecafoot since December 2021 – that was first published by the website Camfoot.com allegedly revealed a plot hatched between the two men.

“There are things we can do, but you have to be very discreet, brother,” Eto’o says in the 11-minute recording in which a man said to be Nkwain – he has denied it was his voice – complained about the officiating and his treatment. “I haven’t even had time to get home yet. I’m out, bro. I haven’t had time to get home and work with the president [of the Cameroonian referees’ association] because I can’t call the refs directly and tell them to be careful. But I can work with the president …

“Opopo must go up to the first division,” he says. “This is our goal. This is our federation. Victoria United will go up. Stay calm, we will grant you the three points and we suspend the referee. But let me at least go back to Cameroon.”

Immediately after that conversation at the start of January, Victoria went on an unbeaten run of 12 matches that included nine victories. What is striking is that in four of those wins their opponents finished with at least one red card. Victoria were also awarded the points in four matches decided by Fecafoot’s disciplinary panel that had been abandoned owing to crowd trouble, including a game at Unisport de Bafang in February that was called off when home supporters invaded the pitch with Victoria trailing 1-0.

That was swiftly followed by the sacking of the goalkeeper Idriss Youssouf in February after he claimed “we buy matches and we will go up”, with Youssouf dismissed on grounds that “he violated article 5(6) of his professional contract which states that he should safeguard the reputation of the club and its members, and respect duty of confidentiality in abstaining from material and prejudicial statements aimed at the club”.

In response to the leak, Eto’o told the Italian newspaper Gazzetta dello Sport in June that he had been “talking to a friend, someone who invests in football and wants to make his club one of the best in Cameroon”. He said: “I just reassured him by saying that I would have done everything possible to avoid any refereeing errors against him.”

Eto’o’s position as Fecafoot president was already under severe pressure after a series of incidents that included a “violent altercation” with an Algerian journalist at the World Cup in Qatar last year. In June 2022, the former striker pleaded guilty to a £3m tax fraud charge relating to his image rights while playing in Spain and was given a suspended 22-month prison sentence and a £1.4m fine – a conviction many have argued should bar him from the presidency.

Eto’o was also heavily criticised for taking an ambassadorial role with a sports betting company and changing the Fecafoot president’s mandate from four to seven years. Some journalists have told the Guardian they are scared to attend press conferences for fear of recriminations over their critical reporting of Eto’o and other Fecafoot officials.

A Confederation of African Football (Caf) investigation into “certain alleged improper conduct” by Eto’o in early August has yet to take any action against him. But a letter sent by several leading football officials last week jointly addressing Fifa’s president, Gianni Infantino, and the Caf president, Patrice Motsepe, that questioned how Eto’o had been allowed to continue “to illegally impose himself on the Fecafoot presidency” prompted police to launch an official investigation into the leaked recording.

Nkwain, who claims to have spent more than £1.3m since taking over at Victoria last year, said in a statement via the club that he did not recognise “this so-called voice message”. “With everything that a popular club like Victoria United does for the South West and Cameroonian football, we cannot accept this manipulation, these lies and this falsification,” the statement said. “Our lawyers are working to file a complaint against the people responsible for circulating these false rumours, so that they can prove the authenticity and source of the voice notes and other information circulating on social media.”

But new evidence presented by Camfoot on Monday could prove to be crucial. It asked the London-based audio experts Earshot to analyse the recording and Earshot found that it had not been manipulated and that the voices belonged to Nkwain and Eto’o. “Nkwain denying the existence of the conversation should have triggered a self-referral to the ethics commission of the Cameroonian Football Federation: nothing has happened to date,” Camfoot wrote. “This independent expert report thus puts an end to all speculation about the authenticity of the audio, Camfoot makes the report available to judicial authorities and the ethics commission of Fecafoot, Caf and Fifa.”

None of those responded to questions from the Guardian. Neither Eto’o nor Nkwain has commented since the police investigation was opened.