Craig Roach, 28, from Yeovil, was discovered by staff at HMP Exeter at 0505 GMT on Sunday after one night in the jail.

Attempts to resuscitate him failed and he was pronounced dead just before 0600 GMT.

The Prison Service said Mr Roach had been on suicide watch while on remand from Taunton Magistrates Court where he had been facing minor shop-lifting charges. He had not been convicted and it was his first time in prison.

Things like this will happen no matter what we do really Gary Ingram, deputy governor

An investigation, led by a senior member of the Prison Service, has been launched and the coroner and next of kin have been informed.

The jail said he had a history of drug abuse and had a potential for self-harm, so he was under extra supervision.

Managers of the prison said they had done as much as possible to prevent a suicide.

'Petty offence'

Gary Ingram, deputy governor, said: "Things like this will happen no matter what we do really.

"There is no way of preventing it other than really degrading measures like keeping someone in total isolation, without access to sheets and thinks like that."

Juliet Lyon, director of the Prison Reform Trust, said: "Far too often things like this happen, particularly with remand prisoners.

"What I cannot understand is why this man, held for a petty offence, was remanded in prison custody .

"Why wasn't he on bail or receiving mental health treatment?"

She added: "Over the weekend three people died in prison. It's absolutely shocking.

"Prison is a last resort for serious offenders and if we insist on sending more and more people to prison, we can't expect our staff to cope."