File photo: Daniels says she slept with Trump during a celebrity golf tournament at Lake Tahoe, California, in 2006. Picture: AP

London - Stormy Daniels has revealed that Donald Trump was the worst lover she’s ever had.

In a tell-all memoir, the former porn star says the US president was her "least impressive" sexual partner.

However, the tycoon "clearly didn’t share that opinion" and thought he was great in bed, Daniels claims.

The 39-year-old also mocks his manhood, comparing it to the mushroom character in the Nintendo video game Mario Kart.

In a vivid and comical description of his "unusual" privates, she refers to them as "smaller than average" but "not freakishly small". 

"It may have been the least impressive sex I’d ever had, but clearly, he didn’t share that opinion she recalls in the book, called Full Disclosure.

Daniels says she slept with Trump during a celebrity golf tournament at Lake Tahoe, California, in 2006.

The president has strongly denied their encounter ever took place. In her book, she writes that for years afterwards whenever she saw Trump on television she would say to herself: "I had sex with that. Eech."

The extracts of Full Disclosure, which is out in October, appeared in The Guardian.