Amazon CEO Jeff Bezos has said the National Enquirer threatened to publish revealing photographs of him unless his private investigators backed off the US tabloid.
Mr Bezos detailed the revelations in a post on the Medium.com website where he said he was the target of "extortion and blackmail" by the publisher of the Enquirer.
American Media Inc (AMI), the Enquirer's parent company, has said it believes it "acted lawfully" but would investigation the claims.
After the tabloid published a story about his extramarital affair last month, Mr Bezos ordered a team of private investigators to get to the bottom of how the Enquirer obtained risque texts between the executive and former TV anchor Lauren Sanchez.
This was followed by the tabloid's editor, Dylan Howard, emailing a lawyer for Mr Bezos' longtime security consultant in order to describe photos the Enquirer "obtained during our newsgathering".
The photos include a "below the belt selfie" of Mr Bezos, photos of him in tight boxer-briefs and wearing only a towel.
There are also several revealing photos of Ms Sanchez, according to the email Mr Bezos released in his blog post.
According to emails Mr Bezos posted, a lawyer for AMI offered a deal on Wednesday - the tabloid would not post the photos if Mr Bezos and his investigators released a public statement "affirming that they have no knowledge or basis" to suggest that the Enquirer's coverage was "politically motivated or influenced by political forces".
Mr Bezos' investigators have suggested the Enquirer's coverage of his affair was politically motivated.
'Sleazy text messages and gushing love notes'
Mr Bezos, who owns the Washington Post, has been the target of criticism from US president Donald Trump over the Post's critical coverage of the White House.
AMI has previously admitted that it engaged in what is known as "catch-and-kill" practices to help Trump become president.
That admission was part of a deal between AMI and federal prosecutors, who agreed to not pursue charges against the company for secretly assisting Mr Trump's campaign by paying 150,000 US dollars (£82,000) to a Playboy model for the rights to her story about an alleged affair with the then-candidate. The company then intentionally suppressed the story until after the election.
Last month, the Enquirer reported that Mr Bezos sent "sleazy text messages and gushing love notes" to Ms Sanchez, months before Mr Bezos announced he was splitting up with his wife, MacKenzie.
Reporters for the Enquirer followed Mr Bezos and Ms Sanchez "across five states and 40,000 miles" and "tailed them in private jets, swanky limos, helicopter rides, romantic hikes, five-star hotel hideaways, intimate dinner dates and 'quality time' in hidden love nests", the tabloid said in its story. The January 9 story carries the bylines of Mr Howard and two reporters.
In his blog post on Thursday, Mr Bezos said he decided to publish the emails sent to his team "rather than capitulate to extortion and blackmail", despite the "personal cost and embarrassment they threaten".
In a statement released on Friday, AMI said: "American Media believes fervently that it acted lawfully in the reporting of the story of Mr Bezos. Further, at the time of the recent allegations made by Mr Bezos, it was in good faith negotiations to resolve all matters with him.
"Nonetheless, in light of the nature of the allegations published by Mr Bezos, the Board has convened and determined that it should promptly and thoroughly investigate the claims.
"Upon completion of that investigation, the Board will take whatever appropriate action is necessary."