Simon Cowell undergoes regular colonic irrigation, it is claimed in a new biography of the X Factor star

Simon Cowell undergoes regular colonic irrigation because he believes it gives his eyes an extra sparkle, a new book claims.

The X Factor supremo is also hooked up to an intravenous drip on a regular basis to flood his body with nutrients, according to the unauthorised biography Sweet Revenge.

Tom Bower’s book suggests Cowell uses a number of unusual methods to hang on to his health and try to retain a youthful look.

The book, which is being serialised by The Sun, has already made claims about the media mogul having an affair with former X Factor judge Dannii Minogue and his unflattering comments about acts and judges from the show.

In a further instalment, the book alleges Cowell undergoes the irrigation process - in which the intestine is flushed out. He is quoted as saying: “It’s so cleansing - and it makes my eyes shine brighter.”

He is also said to be put on a drip for half an hour each week when he is at his US home, supplying a boost to the levels of magnesium and vitamins C and B in his body.

Cowell has for years kept his private life under wraps, with his publicist Max Clifford admitting that he has endeavoured to keep a number of stories out of the spotlight.

But the multimillionaire TV star spoke to Bower during the preparation of the book.

Yesterday Clifford said that agreeing to be interviewed had been a “massive own goal”.

Cowell posted a message on Twitter to point out that this was not an official biography although he did not deny he had taken part in the book’s preparation.

He said: “This book is not written by me. It is unauthorised. The writer is Tom Bower.”

Mr Clifford told ITV’s Daybreak he was “disappointed” that Cowell had agreed to speak to the author.

He said: “Sensation sells and the private lives of the rich and famous is something people in Britain love to read about.

“I don’t think Simon is very happy about it, but Tom Bower was going to do the book whether he spoke to Simon or not.

“We discussed it and I told him to keep well away from Tom Bower, in my view. Once you speak to someone, you’re working with them.

“The book hasn’t done anything that’s going to increase his popularity with anybody. It makes him appear to be someone who talks about his private life. He doesn’t.”