Russia have accused UK Anti-Doping (UKAD) of creating "a wall of mistrust" after they revealed they would block any attempts by the World Anti-Doping Agency (WADA) to seize samples given by Sir Mo Farah during an investigation into athletes trained by the Briton's disgraced former coach Alberto Salazar.
Nicole Sapstead, the chief executive of UKAD, warned last week she would not sanction the release of blood and urine samples from Britain's four-time Olympic gold medallist, unless there was "credible evidence" to suggest they contained banned substances.
UKAD refused a request to hand over those it held for Sir Mo during the United States Anti-Doping Agency's investigation into Salazar, banned in October for four years for doping offences.
They claimed at the time that retesting risked degrading samples which are stored for up to 10 years for testing using new detection methods.
UKAD played a leading role in helping rebuild the anti-doping system in Russia following the publication of a series of reports which led to the Russian Anti-Doping Agency (RUSADA) being suspended initially by WADA in 2016.
Now, RUSADA, currently facing the prospect of having a ban reimposed after allegedly manipulating data from the Moscow Laboratory they transferred to WADA, have called on Britain to be treated the same as everyone else.
"The World Anti-Doping Code and WADA standards are the same for everyone," RUSADA deputy general director Margarita Pakhnotskaya told Russia's official state news agency TASS.
"Be it the British Anti-Doping Agency, RUSADA or some other.
"Otherwise, the system will not work.
"Therefore, I believe that UKAD should not obstruct any transfer of samples.
"According to paragraph 6.5 of the World Anti-Doping Code, the subsequent additional analysis of doping samples can be carried out at any time solely on the instructions of the anti-doping organisation or on the instructions of WADA.
"Any opacity on either side, and this is not just about UKAD, creates a wall of mistrust in the country's anti-doping system and, accordingly, its athletes as part of the system."
Sir Mo, winner of the Olympic 5,000 and 10,000 metres gold medals at London 2012 and Rio 2016, has never failed a drugs test and has always strenuously denied taking banned substances.