Tony Bloom, the billionaire owner of Brighton & Hove Albion FC, is facing questions over claims he was an anonymous gambler behind $70m (£52m) in winnings – which allegedly included bets on his football teams.

Bloom – one of the world’s most successful professional gamblers – is claimed to be the “John Doe” referred to in a US legal case that tried to unmask who has benefited from the lucrative winning streak.

Approached by the Guardian, Bloom declined to answer whether he was the “John Doe” in the court filing issued earlier this year. Bloom denied betting on his own teams or competitions that involve them, and a source close to him described the allegations as “entirely false”.

MPs, including the former shadow sports minister Clive Efford, called on the Football Association (FA) to investigate the allegations.

The Guardian revealed this week that Bloom faces a separate UK court claim that he uses frontmen to place substantial bets for a gambling syndicate he controls – including allegations he used Nigel Farage’s former aide and Reform UK insider, George Cottrell.

The US court case, which has not previously been linked to Bloom, also centres on claims that a gambling syndicate has been using a frontman to mask its role in winning vast sums of money.

Bloom’s syndicate was publicly accused of placing bets on his own football teams by the co-founder of the online gambling company, Rollbit, which brought the US legal action.

Its co-founder, known as Razer, posted the claim on X on 14 November, alleging that Bloom’s syndicate placed bets on his own teams on Rollbit, via a frontman. Since that time, other sources have also made the same claims: that Bloom’s syndicate bet on his own teams and competitions they participate in. That would breach FA rules.

The US legal action was brought in order to seek information which would clarify that the “John Doe”, identified as Bloom’s syndicate on X, received winnings from bets placed by a frontman. The initial application was denied by a judge, but the dispute is ongoing.

He is already under scrutiny because of the separate lawsuit in England which alleged he was using frontmen to place substantial bets for a gambling syndicate he controlled. Frontmen include “footballers, sportsmen and businessmen”, as well as Farage backer Cottrell, the UK court document alleges.

This syndicate bet “predominantly” on football, the UK document claims.

Razer’s X post, and other sources who have spoken to the Guardian, go further, and claim that Bloom’s syndicate bet on his own teams with his knowledge and participation. Bloom declined to answer questions about his involvement with his syndicate.

As well as Brighton, Bloom has a financial interest in Royale Union Saint-Gilloise in Belgium.

A source close to him denied that he and his betting syndicate had placed bets on his football clubs and competitions involving them, and said his betting activities were audited by a leading accountancy firm annually.

This process was “to check and confirm that such bets have not taken place” and had shown Bloom had fully complied with the FA’s betting policies. Bloom follows the same audit procedure in Belgium, the source said.

Bloom is one of a handful of club owners who was given in 2014 a “carve-out” to allow him to carry on gambling, but not on any of his own teams or competitions they take part in. If the allegations made are proved, this could be a breach of FA rules.

Efford, a Labour MP, questioned this controversial exemption and said the FA should investigate.

“No one in a position to influence the outcome of a match or possess inside information can bet on the competition they’re involved in,” he said.

“The FA has to investigate these claims and publish their conclusion. Severe sanctions have been imposed on players for gambling on matches and owners are covered by the same rules so this cannot be ignored.”

Clive Betts, the chair of the all-party parliamentary group on football, said: “It demonstrates a potentially very serious problem and could just be the tip of the iceberg. It needs a thorough and comprehensive investigation from the FA and transparency around the regulations that govern this in the future.”

Iain Duncan Smith, the former leader of the Conservative party, added: “The FA must be much more transparent about their lax policy concerning the use of gambling money in the running of their clubs.”

Bloom is regarded as one of the world’s most successful gamblers, and is known in the industry by the moniker of “The Lizard”.

His gambling collective, the Starlizard Betting Syndicate, is alleged to make about £600m each year, according to the UK court filing.

The claim in England has been started by a former business partner, who has alleged that Bloom owes him his share of gambling profits estimated in the region of $250m.

A source close to Bloom said he intends to file a defence to the high court claim in due course.

Cottrell did not respond when asked for comment.