Troubled pop star Britney Spears tried to kill herself on two separate occasions, according to a new unauthorised biography.

Investigative journalist Ian Halperin makes the claim in his yet-to-be-released book, which he researched over 18 months as an undercover  photographer.

In an interview with American magazine Life & Style, Halperin, who has written biographies on Kurt Cobain and Celine Dion among others, says: 'I spoke with her many times and went to her house.

Troubled: Britney Spears, pictured here in Los Angeles last week, twice attempted suicide, according to new claims

'I will say the suicide attempts are true. I know all the details about both of them.'

An Britney family insider confirmed to the publication that the singer regularly hinted at suicide, and revealed her suicidal tendencies began after the birth of her second son Jayden James in September 2006.

The source says: 'It really became an issue once Jayden was born and it became clear Britney's marriage to Kevin was crumbling.'

Dazed: An insider says Britney is now 'like a zombie'

Fresh claims: Author Ian Halperin spoke to US magazine Life & Style

'That's when she began to say things like "I wish I was dead" or "It'd be better if I could go to sleep and never wake up" on a regular basis.'

'It really seemed like the suicide option was a comfort to her, an escape route in case life became too much to handle.'

Britney's well-documented erratic behaviour has calmed in recent months under the watch of her father and conservator Jamie, but the author believes she's still at risk.

He says: 'I think she's in danger of a catastrophic relapse. Britney herself warned me that with her, it's always two steps forward, one step back.'

Adds the insider: 'She's on major medications. And she's being micro-managed and controlled to the extreme by her parents, the courts and a huge team of doctors and handlers.'

'She's like a zombie now. She's a shell of her old self.'