PRISONERS at one of Britain's toughest jails have been organising their own secret "fight club" behind the backs of prison staff, a report claims today.

Taking their lead from the ultra-violent Brad Pitt movie, Fight Club, the prisoners are said to have been slugging it out with each other in organised combat.

The allegations concern Full Sutton maximum security jail, near York, which holds some of the most dangerous men in Britain.

The Prison Service has denied the claim, made by the Chief Inspector of Prisons, Anne Owers, saying no proof of a fight club has ever been found.

"There are occasional confrontations between prisoners, but these are managed effectively by the prison," said a spokesman for the service yesterday.

But the Inspectorate said: "Cell searches had revealed evidence that some prisoners were being pressurised by other prisoners into fights to clear debts, presumably with betting on participants."

The 1999 film Fight Club told the story of a group of white-collar workers who set up an anarchic secret society based on savage and bloody one-to-one battles.

The claims of the prisoners' attempts to emulate the Hollywood violence emerged after a snap inspection by the Prisons Inspectorate.

The assessors made their unannounced visit to the 600-inmate jail in June as a follow-up to an earlier inspection.

They found levels of violence and bullying were on the increase among prisoners and towards staff.

Only two days before their visit, one inmate had attempted to take a prison officer hostage. This was foiled because the officer made sure the cell door could not be shut, enabling a colleague to summon help.

In her report, Ms Owers, said the safety of staff and prisoners needed to be improved at Full Sutton.

She said: "We found documented evidence that gangs who had been operating on the streets continued to operate in the prison by intimidating other prisoners and attempting to get information about individual officers' addresses and shift times."

She added: "Full Sutton has made progress since our last inspection.

"However, there remain a number of important areas that need to be improved, not least some fundamental aspects of safety.

"It is of considerable concern that the prison is still not performing sufficiently well in this important area."

Responding to the report, the director-general of the Prison Service, Phil Wheatley, agreed that safety was a priority in a high-security jail.

He said: "We acknowledge that the anti-bullying policy is in need of review, and this will take place in the next three months."

He also pointed out that, over the past two years, assaults on prisoners and staff had fallen from 38 to 18.