FIFA has denied claims from the lawyer for Grigory Rodchenkov that the governing body had not made any attempt to contact the former Moscow Laboratory head turned whistleblower.
Jim Walden, the founding member of the Walden Macht & Haran LLP law firm, has repeatedly insisted FIFA had not tried to speak to Rodchenkov regarding his evidence of the involvement of Russian footballers in the nation's doping scheme.
It follows reports that the entire Russian team from the 2014 FIFA World Cup in Brazil were implicated in the McLaren Report and were being investigated.
FIFA secretary general Fatma Samoura insisted world football's governing body had not tried to make contact with Rodchenkov, whose revelations sparked the WADA-commissioned McLaren Report, as it was not normal procedure.
The organisation have now claimed, however, that they tried to do so in November with the help of the World Anti-Doping Agency (WADA) but the attempt proved fruitless as Rodchenkov was unavailable.
FIFA told Agence France-Presse that they would make another attempt once WADA had re-analysed the samples from the database.
This is expected to begin later this month.
Walden has been a vocal critic of FIFA after claiming organisations such as world football's governing body and the International Olympic Committee (IOC) had not done enough to protect Rodchenkov from Russia's retaliation against him.
Rodchenkov has consistently been the victim of attacks from Russian officials, including death threats, since he provided evidence to WADA and the IOC of "systemic manipulation" of anti-doping practices, including at Sochi 2014.
It led to the IOC forcing Russia to compete as neutrals at Pyeongchang 2018.
Walden said earlier this week that the "powerful voices" within the IOC and FIFA "are now aligning to try to discredit or silence Dr. Rodchenkov as the Winter Olympics and the World Cup draw near".
He had previously suggested sporting organisations such as the IOC and FIFA would be happy if Rodchenkov were not available to provide further evidence.
The IOC The IOC hit back by claiming Walden hade made a "ridiculous assertion".
FIFA confirmed last month that it received new information from the WADA about Russian footballers implicated in a database obtained from the Moscow Laboratory.
Names of around 300 athletes included in the database were passed on to the respective International Federations.
FIFA, who promised "appropriate sanctions" against those involved if required, was then contacted by the Russian Football Union (RFU) regarding the database.
The RFU launched their own investigation into the claims last month and insisted they would be willing to help FIFA with their probe.
A spokepserson for the Russian Anti-Doping Agency, which remains non-compliant with the WADA Code, told Russia's state news agency TASS that they would support the RFU investigation.
The doping scandal has led to Vitaly Mutko, banned from the Olympics for life by the IOC, stepping down as head of the Organising Committee for this year's World Cup in Russia.
Mutko has also temporarily stood down as President of the RFU for six months to fight the ban.