David Sullivan has stepped down from his role as joint-chair of West Ham United after being "made aware of the impending publication of serious historic allegations", the club said.
BBC Panorama has been working with The Times on a joint investigation into the allegations made about Mr Sullivan.
"Over decades, he's made millions from pornography, newspapers, and football. The investigation is due to be broadcast and published on Monday," a BBC spokesperson said.
It is understood none of the claims relate to West Ham or any of its operations, the club said, while Mr Sullivan also added that none concern "my more than 30 years in football".
"I have recently become aware that factually incorrect and entirely false, decades-old allegations concerning my personal life are due to be broadcast and published," he said.
"The false allegations levelled against me have been sensationalised by the media. After a lifetime spent building businesses in the adult industry in which I have met thousands of women, it is sadly inevitable that a small number of improper conduct claims are being made against me. I categorically deny these claims."
Mr Sullivan, who made his fortune from owning pornographic magazines and sex shops, went on to say he will sue "the BBC for libel, along with any other media outlet that repeats any libellous allegations".
"I am a private man, and those who personally and professionally know the real David Sullivan, not the caricature invented by the tabloids, know exactly who I am and what I stand for," he said.
"I am absolutely not the person the media has decided to paint me as."
Until his resignation on Saturday, Mr Sullivan was on West Ham's board of directors alongside joint-chairs Czech billionaire Daniel Kretinsky and Vanessa Gold.
In his statement, Mr Sullivan said his decision to resign came as West Ham faces a "challenging and important time" and he didn't want to create any distractions.
"This has been an incredibly painful decision to make, but it is one made out of love, respect, and responsibility toward a football club and a fan base that deserve absolute unity and focus moving forward," he said.
West Ham were relegated from the Premier League last month after 14 years in the top flight.
The club's demotion to the Championship was confirmed on 24 May despite a 3-0 win over Leeds.
The 2025/26 season saw the club sack Graham Potter as coach in September, after the team lost four out of five games.
Off the pitch, the season has been mired by protest, with fans waving red cards on the 16th minute of the game, to mark the 16 years under Mr Sullivan and Baroness Brady.
(c) Sky News 2026: David Sullivan steps down as West Ham joint-chair over 'serious historic allegations'

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