The World Anti-Doping Agency (WADA) said on Thursday it had asked an independent prosecutor to review its handling of the case where 23 Chinese swimmers tested positive for a prescription heart drug.
The organisation will also send a "compliance audit team" to China to "assess the current state of the country's anti-doping program" run by anti-doping body CHINADA.
WADA has faced criticism since media reports at the weekend that the swimmers tested positive for trimetazidine (TMZ) — which can enhance performance — ahead of the Tokyo Olympics in 2021 but were not sanctioned after WADA accepted the argument of Chinese authorities that the case was caused by food contamination.
The head of the United States Anti-Doping Agency (USADA), Travis Tygart, has called the situation a "potential cover-up" — a claim which WADA has strongly rejected.
USADA had called on Tuesday for an "independent investigation: into the case and for an "overhaul" of WADA.
WADA said in a statement on Thursday that it had asked former Swiss public prosecutor Eric Cottier to review their handling of the case.
"WADA’s integrity and reputation is under attack. In the past few days, WADA has been unfairly accused of serious bias in favor of China by not appealing the CHINADA case to the Court of Arbitration for Sport," WADA president Witold Banka said in a statement.
"We continue to reject the false accusations and we are pleased to be able to put these questions into the hands of an experienced, respected and independent prosecutor," Banka said.
WADA said Cottier would be given "full and unfettered" access to all their files and documents on the case and added that he is free to consult with any independent experts as he sees fit.
Cottier has been asked to evaluate if there was any bias shown towards China or "any undue interference or other impropriety" in the handling of the case.
The Swiss lawyer will also be asked to determine if the decision not to challenge or appeal against the verdict of CHINADA, that the cases involved food contamination, was reasonable.
Cottier, who was Attorney General of the Canton de Vaud in Switzerland for 17 years before retiring in 2022 and had previously been a court judge, has been asked to deliver his findings in two months.
The team which will travel to China will also include "independent auditors from the broader anti-doping community".
WADA said the visit was part of its regular compliance monitoring program.
WADA Director General Olivier Niggli said: "While not one shred of evidence has been presented to support any of the allegations made against WADA, we wish to deal with the matter as quickly and as comprehensively as possible so that the matter is appropriately handled in advance of the upcoming Paris Olympic and Paralympic Games."
WADS said they had received requests for the review from a "small number of its stakeholders" and that their decisions had been backed by their executive committee.
USADA had called on Tuesday for major reform to WADA.
"We call on governments and the sport movement to overhaul WADA to ensure a cover-up of positive samples on the eve of the Olympic Games cannot occur ever again," the organisation said.
Britain's Aquatics GB said in a statement it was "extremely concerned" over the matter, adding: "The potential loss of trust and reputational damage to sport is significant and we will be monitoring any further updates and possible resolutions closely."
Beijing has called reports about the case "fake news".
"The relevant reports are fake news and not factual," foreign ministry spokesman Wang Wenbin said on Monday.
