British singer Cheryl Cole was left devastated after she reached out to help her embattled brother and he rejected her offer of support.

The pop star's half-sibling Andrew Tweedy's began a life of crime when he was just 13 years old after he was caught stealing, and he ended up behind bars two years later for knifing a man.

In her new book, Cheryl: My Story, which has been serialised in Britain's The Sun newspaper, the star reveals she begged her elder brother to turn his life around before she married soccer star Ashley Cole in 2006, but he snubbed her.

She writes, "When Andrew was 15 he stabbed someone in a fight. He got six years and was locked up in a young offenders' institution to start with as he was too young for adult jail. When Andrew left prison I assumed being locked up would have taught him a lesson and that he'd put his criminal past behind him and start a new life.

"Unfortunately by the time of my wedding, he was in prison again. I went to see him in prison before the wedding. 'Why can't you stop?' I begged him. 'You're devastating the whole family. Why can't you just change your ways?'

"He shrugged and looked me in the face. 'I'm too far gone.' I left in floods of tears. I had the means to help him now if only he wanted to be helped - but he clearly didn't. That hurt like hell.

"He had 50 convictions by now, and was as addicted to alcohol and drugs as he was to crime. His life was bleak and hopeless."