Russian Anti-Doping Agency (RUSADA) director general Yuri Ganus claimed that "unacceptable" allegations of corruption posted on instant messaging platform Telegram was an attempt to "discredit" his organisation.
A Telegram user called "The post truth" accused Ganus of "conflict of interest and corruption".
It is alleged that Ganus appropriated at least 57 million rubles (£636,000/$801,000/€709,000) for 2018 and 53 million rubles (£591,000/$745,000/€660,000) for 2019.
The user also claimed that Ganus used RUSADA money to pay for taxis and English lessons, while officials were able to take holidays on the pretence that they were international business trips.
At the end of the accusation, it is suggested a criminal case is set to be launched in the near future.
Ganus has rejected all claims, giving an extensive defence against the allegations in a press conference held via Zoom today.
He said that the author of the post had a "misunderstanding" of RUSADA and that there were anti-corruption processes in place which made the claims "impossible".
"There is no singles person that can freely manage the funds," Ganus said.
"Although being director general, I do not have access to transfers, accounts and payments.
"Our system is balanced in such a way so that we can ensure mutual control over parts of the system."
Ganus also sought to directly disprove specific claims, such as the allegation that 11.3 million rubles (£126,000/$160,000/€141,000) was spent on taxis over the past two years.
Instead, he claimed that 96,200 rubles (£1,070/$1,400/€1,200) had been spent on taxis in 2018 and 207,800 rubles (£2,300/$2,900/€2,600) had been spent in 2019.
Branding the allegations a "complete lie", Ganus then suggested they were made in an attempt to discredit RUSADA, especially with the organisation's case at the Court of Arbitration of Sport (CAS) looming.
"The goal of this article is clearly to discredit RUSADA, because they do not like the fact that we are an independent and active organisation," he said.
"We expected such attacks because there are those that are unhappy about what we do.
"The question is, why are they doing it?
"Who is interested in doing that?
"Our agency is participating actively in the international agenda, we have a brilliant young team that we are proud of, and all of that is not appreciated."
Ganus had previously told Russian official state news agency TASS that he would take court action against the allegations.
"I am preparing documents and attracting lawyers," he said.
"The printscreen of this article has been done, we will pursue these people and charge them with everything that is possible."
Ganus became RUSADA secretary general in August 2017 and oversaw the controversial reinstatement of the organisation by the World Anti-Doping Agency (WADA).
The move broke a period of deadlock and leading to access to Moscow Laboratory.
In December, WADA’s Executive Committee approved the recommendation of its Compliance Review Committee (CRC) to again deem RUSADA non-compliant with the World Anti-Doping Code, for failing to provide an "authentic" copy of the laboratory's data.
The CRC has alleged that this data was manipulated before being handed over to investigators, which was a requirement for restoring RUSADA's compliance with the code in September 2018.
Among the sanctions WADA has imposed on RUSADA is a four-year ban on the Russian flag flying at the Olympic Games and World Championships.
Russia has also been barred from bidding for the 2032 Olympic and Paralympic Games and is set to be stripped of any World Championships it has been awarded.
RUSADA has appealed the WADA decision to the CAS.
The national anti-doping organisation was first declared non-compliant in 2015, resulting in the resignation of the director general at the time, Nikita Kamaev.
Kamaev then died of a "massive heart attack" in February 2016.
His death came just two weeks after that of RUSADA founding chairman, Vyacheslav Sinev.
Ganus was appointed to his current role after being chosen as someone who could inspire confidence in a renewed RUSADA and was untarnished by its central role in the doping scandal.
After studying law, he planned to work in law enforcement but ended up in business, including shipping and heavy industry.
Ganus took the helm of RUSADA without any special knowledge of sports or science.