Almost all prison Boards of Visitors have serious concerns about the effects of the spiralling prison population in England and Wales, a new study reveals.

A total of 53 out of 60 boards were "very troubled" by the overcrowding and there are genuine fears that prison riots could break out as a result.

In a quarter of prisons seen by the Prison Reform Trust (PRT), who carried out the study, the visitors witnessed higher levels of unrest and threats to safety.

This must act as a wake-up call to the government to take action to avoid this looming crisis in our jails

Juliet Lyon, Prison Reform Trust

These include escalating numbers of assaults and vandalism to cells.

Chairman of the National Advisory Council of Boards of Visitors (NACBV) ) Brian Baker warned that unless action is taken then overstretched prisons will face "major problems of control".

He said the NACBV had already written to Home Secretary David Blunkett urging that action be taken to alleviate the problem.

The number of inmates has mushroomed to 71,000 - up 4,000 in just 12 months - despite the efforts of Mr Blunkett and Lord Chief Justice Lord Woolf to persuade magistrates not to jail offenders for minor crimes.

Mushroomed

PRT director Juliet Lyon said: "Reports from Boards of Visitors across the country must act as a wake-up call to government to take action to avoid this looming crisis in our jails.

"Prisoners are being shuttled around the system, deposited in overcrowded jails far from home and then dumped back in the community.

"We will all pay a very high price for the damage being done to prisoners and their families.

It's definitely on the verge of a crisis without a doubt

Paul Haley Governor of Chelmsford prison

"Overcrowding has put paid to resettlement and efforts by the Prison Service to prevent reoffending. It is clear that people are spilling out of overcrowded prisons more, not less, likely to offend again."

She called for alternatives to custody to be found for all but the most dangerous or persistent offenders.

The survey also showed 18 prisons were said to have returned to "degrading and inhumane" prison conditions caused by cell sharing and excessive time locked up.

Eleven boards were concerned about damage to mental health, increased self harm and suicide attempts.

In 1991, the average prison population was 45,900. Since 1995, more than 12,000 additional prison places have been provided at a cost of �1.28bn .

'Gross'

At the end of April, 85 of the 138 prisons in England and Wales were overcrowded.

The director general of the Prison Service, Martin Narey, told Newsnight that courts had to get the message that giving criminals very short jail sentences was wasting time and money.

He added that prisoners now being forced to share cells designed for one was a "very troubling" situation.

"I think that doubling up is pretty gross, to be frank, and tonight and every night about 13,000 men are sharing a cell meant for one - and sharing a toilet in that cell.

Campaigners want to see an alternative to custody

"That's not the way I want prisoners to be treated. And the fact that the number of prisoners living in those conditions are having to increase as over crowding increases is very troubling for me."

Paul Haley, Governor of Chelmsford prison told the programme the overcrowding was now critical.

"It's definitely on the verge of a crisis without a doubt," he said.

"Some 71,000 prisoners were locked up at the end of last week and we're just not geared up to cope with those sort of numbers.

"We're definitely in crisis, there's no two ways about it."

The PRT carried out the research with the NACBV and a full report will be produced next month.