German sportswear giant Adidas is ending its sponsorship of the International Association of Athletic Federations (IAAF) in the wake of accusations of doping among its athletes and "embedded corruption" in the organization, according to a published report.

Adidas has been considering ending its relationship ever since the release in November 2015 of the first report of the World Anti-Doping Agency (WADA) that detailed charges of "state-sponsored" doping by athletes in Russia, reports the BBC. A second WADA report concluded that "corruption was embedded" within the IAAF under former president Lamine Diack.

A French criminal investigation is also examining the awarding of venues for World Championships. London is to host the event in 2017. Qatar, the controversial pick to host football's World Cup in 2022, was chosen as the venue for the 2019 IAAF World Championship.

Adidas is the biggest sponsor of the IAAF after the company signed an 11-year agreement with the organization in 2008. At the time of the deal, it was reportedly worth a total of £23m ($33m). But sources tell the BBC that the deal is now substantially more lucrative for the IAAF, and if Adidas backs out, it will cost the organization close to £21m ($30m) over the next five years alone. Neither Adidas nor the IAAF has yet made any comment.

Adidas is reportedly prepared to argue that the IAAF has breached its contract if the organization takes court action to challenge the sportswear manufacturer's decision.

Current IAAF president Sebastian Coe, who replaced Diack in August 2015, has vowed to clean up the organisation and called for sanctions against the Russian Athletics Federation (ARAF). But he served as Diack's vice president for seven years and the second WADA report concluded that the leadership council on which he served "could not have been unaware of the extent of doping in athletics and the non-enforcement of applicable anti-doping rules."

Adidas has found itself in the thick of major sports association in trouble. It was the first major sponsor of FIFA, another organization currently reeling from massive charges of corruption and bribery. Adidas has an agreement with the international soccer administration that runs through 2016. Each four-year football World Cup cycle reportedly costs sponsors $100m (£70m).