Two inquiries are being carried out at the site

The news comes soon after two other prison officers were sacked for sending a hoax note to a prisoner telling him his entire family were dead.

Two separate investigations are now underway at the privately-run jail - one by Securicor the company which runs Parc - and another independent investigation by the Prison Service.

The inquiries follow allegations that a senior officer hit a prisoner while he was handcuffed in his cell.

A spokesman for Parc confirmed that a member of staff had been suspended on full pay.

'Safe environment'

Since it opened in 1997, the controversial jail has been dogged by disturbances and seven suicides.

In 1999, it was criticised in a Prison Inspectorate report after it emerged a racist group with Ku Klux Klan links was running a wing, making it impossible to house black prisoners.

However, the last official report into its running praised the prison and concluded that it was now a safe and stable environment.

At the time, Sir David Ramsbottom said the site had develop good systems to deal with sex offenders and drug addicts in order to cut suicides and bullying among its 800-plus inmates.

Then three weeks ago two officers were sacked for sending an inmate a hoax note informing him that his whole family had been wiped out in a fire.

The warders - who returned 20 minutes later to explain to the prisoner the note had been a joke - were immediately suspended while prison officials conducted an investigation and were subsequently dismissed.