Washington DC - An FBI informant charged with lying about President Joe Biden and his son told investigators he received information about Hunter Biden from Russian intelligence associates, prosecutors said Tuesday in a court filing.

Alexander Smirnov (43), a dual US and Israeli national, was arrested last week and indicted for fabricating claims that Biden's son demanded multi-million-dollar bribes from Ukrainian firm Burisma – on whose board he was serving at the time – to protect it from an investigation when Biden was vice president.

"The misinformation he is spreading is not confined to 2020. He is actively peddling new lies that could impact US elections after meeting with Russian intelligence officials in November," special counsel David Weiss and other prosecutors said in a filing to US District Court of Nevada.

The fallout of Smirnov's false accusation about the Bidens "and fabricated information continue to be felt to this day," they said.

The indictment undermines the impeachment effort against Biden being put together by congressional Republicans, who had touted Smirnov's evidence as proof the Bidens were collectively involved in a criminal enterprise.

The claim that Hunter Biden leveraged his father's name for personal gain has been central to a Republican narrative, pushed heavily by Donald Trump, that Joe Biden is corrupt.

A grand jury indictment filed in federal court last week said that for at least a decade Smirnov was acting as a "confidential human source" for the Federal Bureau of Investigation, providing his handler with information to be used in criminal investigations.

The latest filing appears to suggest that officials connected to Russia's intelligence operation have sought to plant dirt on the Bidens ahead of the 2024 election.

"During his custodial interview on February 14, Smirnov admitted that officials associated with Russian intelligence were involved in passing a story about (Hunter Biden)," prosecutors said.

Last week's indictment says that in June 2020, Smirnov told his US handler for the first time about meetings he claimed had taken place four or five years earlier in which executives from Burisma said they had hired Hunter Biden to "protect us, through his dad, from all kinds of problems."

He told the FBI the executives said "they had specifically paid $5 million each to" Joe Biden and Hunter Biden so that Hunter Biden would "take care of all those issues through his dad."

The document says this refers to a criminal investigation being conducted by the then-Ukrainian prosecutor general into Burisma.

The account was repeated in the Tuesday filing, which said: "The events the Defendant first reported to the handler in June 2020 were fabrications."

"Smirnov transformed his routine and unextraordinary business contacts with Burisma in 2017 and later into bribery allegations against (Joe Biden)... after expressing bias against (Biden) and his candidacy."

Smirnov faces one charge of making a false statement, and one of creating a false and fictitious record, in his dealings with an FBI investigation.

If convicted, he could be jailed up to 25 years.