The Prison Service confirmed yesterday it was preparing to use police cells as an emergency measure to deal with chronic overcrowding.
The drastic step would be the first time in seven years that cells in police stations had been used to house prisoners and would be deeply unpopular with police officers.
Jan Berry, vice chairman of the Police Federation, said: "Whatever happens, this must not take already overstretched police officers off the streets."
A prisons spokeswoman said: "We are looking at the use of police cells as a short-term option and at extending the use of the home detention curfew programme."
The curfew scheme, which allows inmates to go home with electronic tags, may include larger numbers of prisoners with more than a year of their sentences left to serve.
The last time overcrowding forced inmates into police cells was in June 1995 when the jail population stood at 52,000. Since then new prisons have been built, while others have been extended. But there are now a record 71,000 prisoners in England and Wales, and staff are struggling to cope.
Serious disturbances have broken out in the past week at three jails in Nottinghamshire, South Yorkshire and Dorset.
Prison chiefs yesterday denied reports that they were planning to use three new prison ships to tackle the overcrowding crisis.