Lamine Diack, the former president of the governing body of world athletics, offered a deal to delay doping sanctions against 23 Russian athletes in exchange for $1.5m in funding to help a friend win the 2012 Senegalese presidential election, French investigators are due to claim in court on Monday.

The allegation will form the basis of the trial on corruption charges of six former senior figures at the International Association of Athletics Federations, including Diack and his son Papa Massata Diack, that will begin in Paris. Papa Massata Diack told the Guardian last week that the allegation is false.

According to submissions by the French National Financial Prosecutor’s Office (PNF), seen by the Guardian, the Diacks are charged with having “established a veritable organised criminal organisation – of formidable efficiency, specialising in corruption, money laundering and embezzlement”.

The files say the Diacks were involved in a scheme called “full protection”, in which 23 Russian athletes paid between €100,000-€600,000 (between approximately £85,000 and £510,000) to former IAAF figures in exchange for being allowed to compete at the London 2012 Olympics and the 2013 World Athletics Championships in Moscow.

The prosecution will detail alleged links between the Diacks and key Russian government figures, including Vladimir Putin, and say the “full protection” plan was Lamine Diack’s suggestion at a meeting with the then Russian sports minister, Vitaly Mutko, in November 2011.

In December 2014 the German TV station ARD claimed the Russian runner Liliya Shobukhova paid €450,000 to senior IAAF figures in exchange for having her blood passport case slowed down in order to compete in the 2012 Olympic marathon. However, French investigators claim this was just the tip of the iceberg.

Facebook Twitter Pinterest Liliya Shobukhova winning the 2010 London Marathon. She is alleged to have paid to have her blood passport case slowed so she could compete in the 2012 Olympics. Photograph: Sean Dempsey/PA

The revelations led to an independent IAAF investigation during which Papa Massata Diack, a former IAAF marketing consultant, the Russian coach Alexei Melnikov and Valentin Balakhnichev, a former IAAF treasurer, were banned from athletics for life for causing “unprecedented damage” to the sport after being found guilty of corruption, blackmail and extortion charges in 2016. A fourth man, Habib Cissé – who was Lamine Diack’s legal counsel – was banned in September.

After a four-year French judicial investigation, all four men will go on trial in Paris on Monday, along with Lamine Diack and the former IAAF anti-doping chief Gabriel Dollé, who was banned from athletics for five years for his part in the scheme to extort money from athletes. All deny the charges.

Only Lamine Diack, Cissé and Dollé are expected to attend the trial in person. Papa Massata Diack remains in Senegal, after attempts by the French authorities to extradite him failed.

Balakhnichev and Melnikov, the subjects of an international warrant in January 2019, remain in Russia. They deny the charges against them and question the authenticity of the documents and emails.

IAAF bans four senior officials over alleged doping cover-ups Read more

According to French files, Lamine Diack has admitted to investigators that he had offered a deal to the Russians: the postponement of the athletes’ sanctions in exchange for funding the Senegalese presidential election in March 2012.

The files also suggest Diack “solicited Russian aid to oppose the re-election of the outgoing president” of Senegal, Abdoulaye Wade, in 2012 and that he “had requested and obtained funding of $1,500,000”. However, Papa Massata Diack told the Guardian this was not the case. “I totally reject the accusation because my father was not a candidate for the elections. I challenge French justice to prove it. Let’s see what they have at the trial.”

When Lamine Diack was asked to comment on the French investigators’ report, his lawyer, William Bourdon, replied that he “reserves his explanations for the court”.

Cissé’s lawyers say a claim from prosecutors he received €600,000 in fees as a result of his involvement in the scheme is “absurd” because “Habib Cissé, in his capacity as a lawyer, that is to say self-employed and independent of the IAAF, never had any power of supervision over the procedures for suspending suspected doping athletes”.

Dollé apparently admits in the prosecutor’s report that he made the “faux pas of his life” in accepting €190,000 for his part in the scheme. His lawyer did not respond to requests for comment.