It is the second death there this week and the fourth since the prison opened a year ago.

Prison medical staff fought to revive him after he was found on Friday night but they failed, said a spokeswoman for the security firm Securicor.

Michael Rooke from Maesteg, Bridgend, was placed on suicide watch when he was jailed for burglary, taking a car and driving away in October.

His death comes just three days after a remand prisoner, 30-year-old Delvin Bishop-Price, was found hanging in his cell.

The Securicor spokeswoman said: "Deaths in custody are a tragedy for all concerned, which is why Her Majesty's Inspector of Prisons is currently conducting a national review of caring for the suicidal in custody.

"We would like to pass on our condolences to the prisoner's family."

An internal investigation would be carried out along with a Prison Service probe and staff were co-operating with police and the coroner's court, she added.

The 800-prisoner category B jail was the first in the UK to be designed, constructed, managed and financed entirely by the private sector.

The first prisoners arrived on 17 November 1997 and the first suicide came 10 days later. Another prisoner took his life on 5 May this year.