A former informant has pleaded guilty to lying to the US Federal Bureau of Investigation (FBI) about a fake bribery scheme involving President Joe Biden and his son Hunter.

Alexander Smirnov, 44, also admitted tax evasion after not reporting more than $2m (£1.58m) in income.

His claims became the basis of an impeachment investigation in Congress which centred around the false claims that the Bidens made millions in bribes from Burisma, a Ukrainian energy company.

But Smirnov admitted he made the story up, and pleaded guilty in Los Angeles on Monday as part of an agreement with prosecutors.

Smirnov, a dual US-Israeli citizen, had been an FBI informant for more than a decade when he made the allegations about the Bidens in June 2020, saying that Joe and Hunter Biden each received $5m from the energy company.

Prosecutors said Smirnov was motivated by "bias" against President Biden and that he spun his "routine and unextraordinary business contacts" with Burisma into tales about bribery that were "fabrications".

The FBI investigated his statements but within months recommended the case be closed without any legal action taken against the Bidens.

But the allegations refused to die, and became the basis for a Republican-led drive to investigate President Biden, including an effort to make Smirnov's initial statement public.

Prosecutors say that when he was re-interviewed by FBI agents in September 2023, Smirnov doubled down on his claims.

Smirnov was arrested in Nevada as he returned to the US from an overseas trip in February 2024.

• Alexander Smirnov: FBI source accused of Biden lies 'linked to Russian intelligence'

According to court documents, he had ties with Russian intelligence and used his more than $2m in unreported income to buy a Las Vegas condominium, a lease on a Bentley car, and hundreds of thousands of dollars of clothes, jewellery and accessories.

The case was brought by Special Counsel David Weiss - who has overseen an investigation of Hunter Biden.

Joe Biden issued a pardon for his son, who faced potential prison time for tax evasion and lying on a form about his drug addiction when he bought a gun.

Smirnov will be sentenced in January. The plea agreement is subject to approval by a federal judge.

He faces a maximum sentence of 35 years in prison and a $1m fine, however prosecutors and defence lawyers have agreed to a sentence of between four and six years and a restitution payment of $675,502, according to the plea deal.

The BBC contacted Smirnov's lawyers for comment.