Controversial open-ended prison sentences introduced to protect the public may have to be scrapped after inspectors warned that their cost to the penal system outweighed any benefits.
Just 75 of almost 6,000 convicts held under the indeterminate sentence for public protection (IPP) have won their liberty since the measure was brought in by Labour four years ago.
The result, said Chief Inspector of Probation, Andrew Bridges, and the Chief Inspector of Prisons, Anne Owers, is that prisons have become swamped with inmates whom the probation service did not have the resources to deal with. They warned that the situation has become "unsustainable" and called on ministers to begin a major review of the policy.
Mr Bridges said: "A high number of prisoners remain in the system and continue to enter it. There will continue to be huge numbers of such prisoners that neither the probation service nor the prison system currently has the capacity to handle effectively.
"We consider that the present position is unsustainable. This suggests the need for a major policy review at ministerial level. Such a review would need to consider whether the resources needed to manage these sentences properly are proportionate to the benefits they might achieve."
The inspectors' first report, published in September 2008, concluded that the surge of prisoners subject to the new sentences was flooding the prison system. Today's report expresses doubts about probation's capacity to work effectively with each case when the number of prisoners still coming through the system is so great.
The report was welcomed by prison reform groups, who said the IPP was pushing the prison system to breaking point. In 2008, the Joint Committee on Human Rights, in response to evidence submitted by the Prison Reform Trust, said it was deeply concerned by the effect of IPP sentences on some prisoners.
A number of MPs have taken up the concerns of their constituents who find themselves affected by the IPP sentence. Andrew Stunnell MP will today table an early day motion on the issue following the Inspectorates' joint report and submissions made by the Prison Reform Trust.
Commenting on the findings of the review, Juliet Lyon, director of the Prison Reform Trust, said: "This review offers further evidence of the chaos the ill-thought-out IPP sentence has caused in the criminal justice system. The Government's response has veered between bravado and blankness.
"On the one hand it has boasted publicly about its toughness in introducing the sentence.
"On the other it has blanked out the damage to individuals and their families trapped in a maze with no exit, and ignored the operational chaos caused on prison landings by the massive new load the sentence entails."
She added: "While you can never eradicate risk, it must be possible to identify the few genuinely dangerous people amongst the thousands we stack up and leave to rot on indeterminate jail sentences, which in itself is a dangerous and stupid thing to do.
"The Government has played gesture politics while neglecting its management responsibilities to the prison system."
IPP prisoners make up one in 15 of the total prison population, but managing them through their sentences is more resource-intensive than work with those on fixed-term sentences.
A Ministry of Justice spokesman said IPP sentences were introduced to make sure that violent and dangerous offenders can only be released by the Parole Board if they no longer pose a threat to society.
"We recognise that this means that prisoners could remain in prison for many years beyond the minimum term set by the judge. Indeed, these sentences are an important part of a strategy on tackling crime which has seen crime fall by almost 40 per cent since 1997."
He added: "The Government keeps all sentences under review to ensure they are operating effectively, and we welcome the Chief Inspectors' recommendations for further improvements."