Criminals will be held in police cells in an emergency measure introduced to deal with a bursting prison population, John Reid has announced.
The home secretary today confirmed there are currently 79,819 people in jail in England and Wales, just 149 places short of full capacity.
As a result, Mr Reid has ordered the implementation of Operation Safeguard, which was last used in 2002 and will see sentenced criminals held in police cells.
"The use of [the] safeguard is not ideal but it is tried and it is tested," he told the House of Commons this afternoon, saying he was "extremely grateful" for the police's support.
However, the Police Federation, which represents rank and file officers, today expressed "grave fears" about the practical implications of this policy.
"Not least because the resilience of the service is already stretched to breaking point but being a full-time jailer requires a completely different set of skills and training to that of being a police officer," said vice chairman Alan Gordon.
Shadow home secretary David Davis condemned the "sorry handling of this crisis in our prison system" and warned that the use of prison cells was impractical and expensive - in 2002, it cost £10 million, he said.
Ministers should have acted on the problem of overcrowding years ago, he said, adding: "Why do we have to get to a crisis to get action out of this government?"
Mr Reid accepted personal responsibility for the problem but insisted it was not a crisis, accusing the Tories of making a "dreadful fuss because we're a couple of hundred short of prison places".
The home secretary blamed two events for the sharp rise in the prison population this summer, including the foreign prisoners scandal, after which he promised to detain all foreign nationals convicted of crimes until they could be considered for deportation.
Secondly, he said that although judges were putting into effect their new powers to give indeterminate sentences under the Criminal Justice Act 2003, they were not yet using the power under that law to give more community orders "as fully as they might".
As well as Operation Safeguard, Mr Reid has ordered two women's prisons to be converted into men's prisons and the transfer of some prisoners to open prisons. This would not include those guilty of violent or sexual crimes.
Negotiations are also ongoing to convert a former army barracks and a former secure hospital at Ashworth East near Liverpool into prisons. In addition to the extra 8,000 prison places Mr Reid announced this summer, there will be another 700 by 2008.