X Factor boss Simon Cowell told the actor who is to play him in a new musical: "Just go out there and be a d**k every night."

I Can't Sing! The X Factor Musical, penned by TV Burp's Harry Hill, has received Cowell's financial backing despite its savage lampooning of the song contest.

For authenticity's sake, Cowell advised leading man Nigel Harman, of EastEnders and Downton Abbey fame, to play up his trademark rudeness.

The 54-year-old mogul told The Sunday Times Culture supplement: "We had lots of people trying to do really serious versions of the show, but we just turned them down.

"When Harry used to take the p**s out of us on TV Burp, we all wanted to be the one he parodied.

"He knew we had banned the word 'journey' - they're not on a journey, they're on a talent show for a couple of weeks, so we fined anyone who used the word 'journey'.

"Then we banned the word 'dream' because it was getting out of control.

"Of course, when he pitched it to me, the first song they played was called Journey to a Dream. It made me laugh and I was in."

Speaking before the birth of his son Eric on Valentine's Day, Cowell added: "The deal I made with Harry was, 'I'm not going to change a word'.

"It is what it is. If it looks like I had an influence, it won't work."

The musical takes its inspiration from X Factor's chaotic 2010 season, which saw judge Cheryl Cole battle malaria, race rows, contestants with mental health and visa problems, and ludicrous performances.

Commenting on the show's thinly-veiled portrayal of Cole as a character called Jordy, Cowell said: "Cheryl is going to kill me when she sees it. I mean, seriously, I'm going to get it in the neck."

Harman explained that while he imitates classic Cowell mannerisms such as the way he stands and uses his hands, the performance delves into "a whole new realm of farce".

"People will sit in the audience and go 'I can't believe he's allowed this to happen,'" the 40-year-old said.

I Can't Sing! previews at the London Palladium from Thursday.