Some of Britain's most disturbed prisoners are being deprived of mental stimulation and human contact, according to a report.

Britain's most notoriously disruptive inmate Charles Bronson is among a hard-core of prisoners locked up in specialist units because of their dangerous behaviour.

An austere regime for about 40 men kept in close supervision centres at Woodhill and Durham jails means many of them do not see another human face for months.

But a report by the Prisons' Inspectorate recommends that prisoners locked up in Britain's "Alcatraz" should be kept in better conditions to prevent them becoming more disruptive.

A handful of the most disturbed inmates at Woodhill, at Milton Keynes, Buckinghamshire, are rarely allowed out of their cells and are met by six officers in full protective gear and helmets when they are let out.

Punishment conditions

Inmates in the segregation unit - "D-wing"- live in "total isolation in punishment conditions" with only an hour's respite a day.

The report concludes that "prisoners were chronically socially isolated and under-stimulated".

Specialist unit regimes

Specialist units opened in 1998 There are currently 46 inmates Cells have a cardboard table and chair Radios and photos are not allowed Food is passed through secure hatches Bed is a concrete plinth with a mattress Only two inmates at a time allowed out of their cells to shower or for exercise in a caged yard Longest continuous stay on D-wing was seven months

Restrictions mean that contact with friends and families is rare, with little exposure to the "humanising influence" of people who care for them.

The report recommends that prisoners should be allowed to keep study material, clothing and other property that other mainstream prisoners are allowed.

The report say the stark regime has not worked for some inmates who "continue to resist, and may indeed regress".

It concludes: "The regime operating in D-wing in Woodhill which imposes total and continuing isolation in punishment conditions for unlimited periods is unacceptable."

Chief Inspector of Prisons Sir David Ramsbotham said: "We need to find a way of holding them in terms of conditions that are acceptable but not seen to reward outrageous dangerous behaviour."

He called for an independent monitoring group to scrutinise the close supervision centre system.

Prison Service Director General Martin Narey welcomed the report and said he would give "serious consideration" to the comments.

He highlighted the difference between England and Wales, where 46 inmates were subjected to the regime, and the US, where there were 18,000 in similar conditions.

"The management of the most difficult and dangerous prisoners presents a major problem for countries throughout the world," he said.

"We have not always got the balance right and I will give serious consideration to the chief inspector's comments."

Many of the prisoners in the specialist units are convicted killers, but their behaviour behind bars marked them out for special treatment.

Five had been convicted of killing while in jail, three had taken hostages and others were involved in serious disturbances.