The Investigative Committee said Wednesday that anti-corruption activist Alexei Navalny fraudulently obtained his credentials as a lawyer.
The accusation against one of Russia's most prominent opposition figures is the latest in a series of blows traded between Navalny and the powerful Investigative Committee.
"To meet the requirement for two years of legal experience, which is mandatory to receive status as a lawyer," Navalny said in his application documents that he was the deputy director responsible for legal issues at Allekt, a company where he was also director, the Investigative Committee said in a statement posted on its website.
"So he named himself both director and his own deputy," the statement said.
The statement goes on to say that the company Allekt did not even exist during the period when Navalny says he gained legal experience there.
The official accusation comes 48 hours after state-controlled television channel NTV aired a short documentary film which, based on a blog post by blogger and journalist Maxim Kononenko, suggested Navalny's lawyer status was obtained under false pretenses.
Navalny became a lawyer in 2009 while he was working as an adviser to Nikita Belykh, the governor of the Kirov region. Belykh is one of a group of prominent opposition figures, including Navalny, that have been tangled up in criminal investigations in recent months.
The Investigative Committee, which Navalny has repeatedly accused of being a political tool, was ridiculed by the anti-corruption activist in a blog post that said the allegations were old and baseless.
"So far all these complaints have been unsuccessful because they contain a load of rubbish that is instantly exposed under critical examination," Navalny said.
The Moscow Legal Chamber, which registers lawyers in the capital, said it would conduct its own check into Navalny's status, the RAPSI news agency reported.
Two years of legal experience is just one of the requirements for becoming a lawyer.
Navalny said he had been summoned by the Investigative Committee for questioning Wednesday at midday.
The alleged irregularities concerning Navalny's lawyer status were uncovered as part of an ongoing criminal investigation into Navalny's involvement with the theft of timber from the state-owned KirovLes company in 2009, the Investigative Committee said.
The news of the Investigative Committee's accusations against Navalny was first made public on Wednesday morning through the newly-opened Twitter account of Investigative Committee spokesman Vladimir Markin.