The U.S. Anti-Doping Agency (USADA) criticised the World Anti-Doping Agency (WADA) on Wednesday for "doubling down on half-truths", after the global body published a document outlining its handling of a case involving Chinese swimmers.

WADA has been under fire since the New York Times reported last month that 23 Chinese swimmers tested positive for trimetazidine (TMZ) ahead of the Tokyo Games in 2021 but were allowed to compete after being cleared by a Chinese inquiry.

WADA accepted the findings of a Chinese investigation that the swimmers were inadvertently exposed to the drug and the case was not made public.

In a "frequently asked questions" (FAQ) document released days ago, WADA said there were "strong indicators that these cases could be a case of group contamination."

"The facts and intelligence also support a finding of coordinated intentional doping such that WADA should have initiated an investigation into the source of these positive tests," USADA wrote on Wednesday.

"But it did not, failing all clean athletes."

A WADA spokesperson said the organisation stands by the contents of its FAQ sheet and that it "followed every process and line of inquiry when reviewing this file".

"Based on the science and the verifiable facts, as well as external legal counsel, (WADA) decided not to take what inevitably would have been a doomed appeal to the Court of Arbitration for Sport," the spokesperson said in a statement.

"To this day, no evidence has been produced that would change our position on that. Very serious and defamatory allegations continue to be made about WADA without so much as a shred of supporting evidence. WADA continues to reject those allegations as entirely baseless."

USADA's 16-page document outlined a wide array of concerns and is the latest salvo in a public spat between the two sides.

WADA said last week that it would launch an independent review over its handling of the case amid a widespread backlash, after USADA called for a complete overhaul of the global body to restore confidence ahead of the Paris Games.

"The doubling down on half-truths and self-serving rationalizations for failing to enforce its own rules is deeply concerning," USADA said. "Those who value fair play remain completely unsatisfied by the answers being provided by WADA regarding its sweeping of 23 positive tests under the carpet."