The World Anti-Doping Agency (Wada) will launch an independent review after 23 Chinese swimmers were cleared to compete at the Tokyo Olympics despite testing positive for a banned substance.

Wada has said it was “not in a position to disprove” an assertion from the China Anti-Doping Agency (Chinada) that contamination was the source of the heart medication trimetazidine (TMZ) for which the swimmers tested positive.

Findings of the investigation, led by Swiss prosecutor Eric Cottier, are expected to be delivered within two months.

“Wada’s integrity and reputation is under attack,” said Wada president Witold Banka.

“Wada has been unfairly accused of bias in favour of China by not appealing the Chinada case to the Court of Arbitration for Sport.

“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.”

United States Anti-Doping Agency (Usada) chief executive Travis Tygart said Wada and Chinada had “swept these positives under the carpet” – claims Wada described as “completely false and defamatory” while adding that it had referred the comments to its lawyers.

Aquatics GB said it was “extremely concerned” by the allegations about the positive tests, which it said threatened “potential loss of trust and reputational damage to sport”.