Lily Allen claims she had sex with a friend of her father's when she was just 14.

Lily Allen

Lily Allen

The 33-year-old singer says she met the unnamed 19-year-old celebrity at a charity football match he played with her dad, Keith Allen, before he bought her drinks and had sex with her and she was horrified when her father and his pals treated it as a joke.

She writes in her new book 'My Thoughts Exactly': "After the match, the TV star left his football gear in my dad's car, and I was dispatched to his hotel to return it.

"We arranged to meet in the bar there. He bought me a couple of drinks, then took me up to his room and had sex with me. I was 14. He was 19, but to me he seemed like someone from a different generation.

"Afterwards, I felt funny about it. I knew what had happened wasn't right.

"My dad turned it into a shtick with his friends. They made up elaborate schemes to blackmail the guy and they rehearsed how they'd call him up and put the s**ts up him. I just know that my dad turned me having sex with this guy I hardly knew into a joke between him and his mates. That didn't make me feel good."

Meanwhile, Lily recently admitted her father has been unhappy with some of the shock claims she has made in her book, including the allegation that he suffered a cocaine-induced heart attack at Glastonbury when Lily was 13.

After hearing about the claims, Keith texted his daughter to furiously deny his collapse was due to drugs.

Speaking on the 'Jonathan Ross Show', Lily said: "I got quite a cross text from him this weekend.

"He texted me, 'Er, cocaine-induced heart attack at Glastonbury. Wow'. And I said, 'Sorry, that's what I thought. I'm really sorry if I got that wrong but that's how I remembered it and you never explained it to me any other way'.

"And he said, 'Well, that's not true'.

"I said, 'I'm really, really sorry if I got that wrong. What was it?' And he said, 'Acute food poisoning'."