Stormy Daniels has claimed Donald Trump offered to help her cheat on the Apprentice as she revealed salacious new details of their alleged affair.

In a tell-all book, the porn star claimed Mr Trump offered to bring her onto his reality TV show The Apprentice and help her cheat to prevent her being knocked out.

Ms Daniels, real name Stephanie Clifford, also gives disparaging details about his genitals and physical appearance as she describes their alleged tryst in 2006.

In her book, Full Disclosure, a copy of which was seen by The Guardian, Ms Daniels claims Mr Trump repeatedly called her over the next year promising to put her on The Apprentice. 

She claims he even suggested a strategy to allow her to survive through several episodes, saying "he was going to have me cheat, and it was 100 percent his idea".

“We’ll figure out a way to get you the challenges beforehand,” she quotes him as saying. 

Ms Daniels goes on to write that for years afterwards the sight of Mr Trump on television for years caused her to think: “‘I had sex with that’, I’d say to myself. Eech.”

The porn star recounts meeting Mr Trump at a celebrity golf tournament in Lake Tahoe, California in 2006 and being invited to dinner in his penthouse suite.

“It may have been the least impressive sex I’d ever had, but clearly, he didn’t share that opinion," she wrote.

Ms Daniels claims that shortly before they had sex, Mr Trump received a call from Hillary Clinton, who was then running against Barack Obama to be the Democratic presidential nominee.

She says the pair were watching a programme about sharks at the time.

“He had a whole conversation about the race, repeatedly mentioning ‘our plan’…Even while he was on the phone with Hillary, his attention kept going back to the sharks,” she writes.

The president has vehemently denied having an affair with Ms Daniels but admitted reimbursing his lawyer for a $130,000 hush-money payment to the adult entertainer shortly before the 2016 election.

Mr Trump’s lawyer, Michael Cohen, has since said the payment constituted a campaign contribution and pleaded guilty to a campaign finance violation.  

Ms Daniels’ memoir, which is released on October 2, comes weeks after another book, veteran journalist Bob Woodward’s Fear, painted a portrait of a White House in turmoil as it struggled against an incompetent president.

Publishers Simon & Schuster announced on Tuesday that Fear has sold more than 1.1 million copies just a week after publication, making it among the fastest selling hardcover books in memory.