The UK Anti-Doping Agency is poised to launch an investigation into allegations that a member of Tyson Fury’s team offered a farmer £25,000 to provide a false alibi after the heavyweight champion failed a drugs test in 2015.

Fury, the WBC heavyweight champion, and his cousin Hughie, both blamed their positive tests for nandrolone on eating uncastrated wild boar or ingesting contaminated supplements – citing two statements from the Preston farmer Martin Carefoot saying he had given them the meat in their defence. However, Carefoot now says he provided two false statements after being offered a financial inducement by a member of Fury’s team to lie.

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Both fighters received backdated doping bans of two years in December 2017, enabling both men to return the ring soon after. Last month Tyson completed an astonishing comeback from drink and drug problems by defeating Deontay Wilder to become a world heavyweight champion once more – and has since been a favourite to win the BBC’s sports personality of the year award.

However, the Furys’ careers could be on the line if Ukad finds the account of Carefoot, given to the Mail on Sunday, to be credible. Both men could face charges of “tampering with an investigation” – and because it would count as a fresh case, they could receive as much as an eight-year ban if found guilty.

In a statement, Ukad said: “We will always review any potential evidence in relation to any anti-doping offence, and take investigatory action where necessary. If anyone has information that could be of interest to Ukad and its investigations on any matter, we urge them to contact us.”

While the cousins insisted to Ukad investigators during the original case that they never intentionally cheated, Carefoot says that he was visited in November 2016 by a friend who knew a member of the Fury entourage. Carefoot alleges he was asked to lie by saying he sourced the boar for the Furys, despite having never delivered boar to them.

Carefoot also signed two witness statements confirming he had been the supplier to Team Fury, which were forwarded to Ukad via lawyers and the Mail on Sunday said it had seen.

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According to the paper, the second statement included a line that read: “I supplied a range of animal meats and offal to Team Fury, including wild boar and pigs.” Carefoot now claims those statements were lies, telling the paper: “I have never kept wild boar. I have never killed a wild boar.” When asked if he had been willing to commit perjury for the Furys, Carefoot said: “I suppose if I’d had to. I was in too deep. They were dangling this carrot. I thought, you’re going to get 25 grand for this, it’s not a hanging matter. So I went along with it.”

Carefoot, who says he was never paid the money he claims he was promised, also told the paper: “I feel sick of the lies and deceit and the public need to know the truth.”

Neither Fury has commented on the allegations, but their management team MTK has been asked for a response. However, Tyson Fury’s promoter Frank Warren insisted the claims were false and he didn’t expect them to go any further.

“Tyson has never ever met this man and his story is total bullshit,” he said. “The farmer making these outrageous allegations sent me a letter last October, full of errors and basically telling me he had committed perjury by signing statements under oath and lying. When I called him, he asked for money. I told him to clear off and get in contact with Ukad. He chose not to speak to Ukad but instead speak to a newspaper.

“How anybody can take this man seriously is beyond belief. We’ll leave this with Ukad to look into and don’t expect it to go any further. It looks like while the football season has been paused, there’s nothing to write about and silly season has instead commenced.”

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Mauricio Sulaiman, president of the World Boxing Council whose belt Fury won from Wilder in Las Vegas last month, said the allegations would have “no impact” on his reign as champion.

“Personally, I prefer to believe Tyson Fury ahead of someone who has already admitted to lying in legal documents for financial gain,” Sulaiman said. “The person who has claimed he accepted money to lie should be the one on trial, in my personal opinion, especially when he has waited five years to tell his story.

“Secondly, around this time Tyson was not involved with the WBC, he did not fight Klitschko for the WBC belt, it was for other titles, so this issue does not impact on him being our heavyweight world champion.”

Fury’s weekend plans to run a half marathon were curtailed by coronavirus but the fighter made no reference to the claims in a post in Instagram on Sunday morning. Under a picture in which he and a friend posed in Batman and Robin outfits, Fury wrote: “We was doing a half marathon today but got cancel for ovs [sic] reasons, but we gonna do a half marathon at home, Batman & robin.”