WASHINGTON (AFP) - Hustler Magazine publisher Larry Flynt has offered US$10 million (S$13.4 million) for dirt to help remove from office US President Donald Trump, in a full-page ad in the Washington Post.

"I do not expect any of Trump's billionaire cronies to rat him out, but I am confident that there are many people in the know for whom US$10 million is a lot of money," he said in the ad.

The porn magazine founder noted that he had used million-dollar cash rewards before to elicit information that helped upend the careers of two Republican politicians.

"For the current crisis, I have upped the ante to US$10 million," he wrote. "Make no mistake, I fully intend to pay this entire sum."

The top of the ad, written in all caps, reads simply: "$10 MILLION FOR INFORMATION LEADING TO THE IMPEACHMENT AND REMOVAL FROM OFFICE OF DONALD J. TRUMP."

It goes on to question the legitimacy of Trump's election and lists offences ranging from Trump's alleged collusion with Russian meddling in the US election to his sabotaging the Paris climate accord.

"But most worrisome is that, long before climate-change apocalypse strikes, Trump might trigger a nuclear world war," he wrote.

"Impeachment would be a messy, contentious affair, but the alternative - three more years of destabilising dysfunction - is worse."

The ad lists an e-mail contact and a hotline, which the Post reported would be staffed on weekdays, 8.30am to 6pm, for the next two weeks.