More than 25,000 prisoners will be released in the next year under an emergency plan announced by the Government today to ease chronic prison overcrowding in England and Wales.
Lord Falconer, the Justice Secretary, told the House of Lords that offenders serving terms of between four weeks and four years in prison would be eligible for release 18 days before their scheduled release date.
The Ministry of Justice said that an estimated 25,500 prisoners will be eligible for early release under the new rules within a year, freeing up an average of 1,200 prison places over that period. The system will come into effect next Friday, at which time between 1,500 and 1,800 prisoners will be freed.
Prisoners will only be granted an early release after a risk assessment in prison but those to be freed will include criminals such as burglars, fraudsters and drug-dealers.
Today's admission - confirming a report in The Times - represents a humiliating U-turn by Lord Falconer, as it comes only a month after he dismissed as "simply wrong" reports that he was considering releasing prisoners early because of a lack of space in jails.
In his statement, the Justice Secretary said that the Government's long-term plan to create 8,000 new prison places still stood, and added that an additional 1,500 places would be built on top of that using new Treasury funding. Work would start on building 500 of those places immediately, he added.
Probation officers and Opposition MPs sharply condemned the move, however, and said that the Government had been warned for years that Britain's jails were filling up dangerously.
"This is a temporary measure. Release on licence is not the same as executive release. Releasing people on licence means their sentence continues," Lord Falconer said.
"The criteria exclude offenders convicted of serious sexual or violent crimes, those who have broken the terms of temporary release in the past and foreign national prisoners who would be subject to deportation at the end of their sentence."
He added: "Whilst on licence the offender will remain the subject of his sentence and will be liable to recall."
The Justice Secretary said the guidance to prison governors to undertake the measure will come into effect on June 29.
The dramatic action comes as the jail population in England and Wales stands at 81,016, a new record, and close to absolute capacity. Some prisoners are being held in police or court cells, usually only used by officers to temporarily detain offenders, because there is nowhere else to put them. Lord Falconer said today that this situation would continue "until the end of the year at the latest".
Harry Fletcher, assistant general secretary of the probation union Napo, said today that the problem was "of the Government's own making".
"It has known that prison numbers have been predicted to rise for the last 10 years, yet they did not build more jails, did not ensure that less offenders were sent down, and they failed to fund alternatives to custody," he said.
The Opposition also sharply criticised the Government's decision today. Speaking in the House of Commons this afternoon after a statement to MPs by the Prisons Minister David Hanson, the Tory spokesman Edward Garnier said: "What we have seen today is the Government doing a total U-turn on early release within a matter of weeks, and it is the public that will pay the price with their safety."
In a separate statement David Davis, the Shadow Home Secretary, said: "This is disgraceful and a direct consequence of the Government's absolute failure to deal with the crises in our prisons."
Simon Hughes, the Liberal Democrat justice spokesman, added: "Creating thousands more offences, sending thousands more people to prison and then releasing others before they have served their time is the criminal justice policy of the madhouse."
Gordon Brown, the Prime Minister-in-waiting, attempted to limit political damage by today's announcement by pledging that the problem would be solved. "What I have been looking at in the last few weeks is how we can build more prison places - we have set aside money for 8,000 more next year - and how we can advance the number of prison places that are provided," he told GMTV before later repeating his pledge at a speech to the Association of Chief Police Officers (ACPO).
Last night, prison staff were bracing themselves for another surge in the numbers held in the 141 jails in England and Wales after police arrests over the weekend.
Six sets of court cells were on standby to hold offenders in case there was not enough space in prisons and in emergency cells at police stations. It is estimated to have cost £30 million since last October to hold prisoners in police and court cells.
Whitehall sources said there was still "tremendous sensitivity" within the Government about early release, but also a growing recognition that it was unsustainable to hold hundreds of offenders in police and court cells. Ministers are particularly worried about the effect the scheme could have on public confidence in the criminal justice system and the Government's record on law and order.
Charles Bushell, the general secretary of the Prison Governors' Association, said he recognised that some people would object to early releases but added that public money was at stake.
"These people are also taxpayers, who are paying through the nose - we reckon over £30 million since last September - simply and solely to ensure that a minister does not have to make an unpalatable decision.
"What we have done over an extended period of time is to enact more and more legislation, locking up more and more prisoners for longer and longer without first ensuring that we have got the spaces to hold these people."
Last Sunday the PGA, which represents the senior managers of the 139 jails in England and Wales, announced that it was in official dispute for the first time in his history. It has told the Ministry of Justice that it is advising its members not to supervise the 24 prisoners being kept overnight and at weekends in court cells.