Dan Carter and Joe Rokocoko are said to be "disgusted and sickened" by leaks to a French newspaper that they returned positive doping samples after the Top 14 final last season.
The two former All Blacks, who play for French club Racing 92, fully expect to be exonerated by French Rugby Federation investigation into the claims, according to their club.
L'Equipe, the French sports newspaper, alleged "traces of corticosteroids" were found in the urine samples produced by Carter, Rokocoko and Racing team-mate Juan Imhoff when they were tested by the French anti-doping agency after the fixture against Toulon, which was played at the Nou Camp in Barcelona in June.
It's understood that the French Anti-Doping Agency, who had special dispensation to carry out the tests as the final took place in Spain, took samples from every player from both the Racing and Toulon squads after the final, which the Paris club won 29-21, with Carter named man of the match.
Simon Porter, an Auckland-based player agent with Essentially Group, the management company representing Carter and Rokocoko, said on Friday the pair had Therapeutic Use Exemption to allow for treatment with cortisone as they recovered from injury.
Carter was receiving medication for a calf injury, Porter said, while Rokocoko was recovering from an ankle problem. Corticosteroids are used to help reduce inflammation.
But Racing 92 appeared to contradict Porter's assertion the players had TUEs when the club said it believed it was not required as their treatment had been administered "several days" before the Top 14 final.
It's understood the confusion arose after Porter was assured by the club everything was under control and Porter assumed this meant they had TUEs.
The French club are adamant they have all medical records of the treatments, which they claim were administered out of competition and within international anti-doping rules.
Their claims are backed up by the fact that, although the FRF have 40 days to investigate, none of the three players has been suspended, as they would be if it was suspected that they had committed a doping violation.
Carter is injured, but Imhoff and Rokocoko were both due to play for Racing in the Paris derby against Stade Francais tonight (NZT).
"All the medical acts carried out on the players cited by the media have been in total respect of national and international anti-doping rules, as well as in the sense of administrative and medical procedures," Racing said in a statement. "It is treatment administered in an authorised manner, provided in response to proven pathologies, several days before the Top 14 final and not needing a TUE.
"Racing 92 will collaborate with all the relevant medical investigative authorities in order for the debate to subside and so everyone is given a full understanding. All the medical protocols are clear. Transparency will be total. We're on the side of those who fight for a clean and respectful sport. Juan Imhoff, Joe Rokocoko and Dan Carter are everyday examples of behaviour, generosity and ethics."
Agustin Pichot, the new vice-chairman of World Rugby, said the game could not afford any complacency in the battle against drug abuse.
"Without knowing the precise details of this case, we have to make sure rugby is a very clean game," Pichot said. "What happened in the Top 14 final, you have to be very careful that everything is in place, TUE or whatever.The protocol must be followed. You have to be clean. The players are innocent until shown to be guilty.
"We have to be very careful that this money-seeking, fame-seeking, evolution-seeking of the sport does not turn against the culture of the game. That is why we have to work hard at World Rugby to ensure it is clean and there is a lot going on to that end at the moment, and we have to be very tough with it. And the leagues have to be very tough."