Home Secretary John Reid has been accused of panic measures over plans to use prison ships to ease overcrowding in jails in England and Wales.
HMP Weare, off the Dorset coast, closed last year
The government has advertised for contractors to provide up to 800 places on ships.
Prison charities said the ships would not meet inmates' needs and Mr Reid would be to blame for people coming out of jail and committing more crimes.
Critics say ministers are lurching from one stop-gap solution to another.
The news comes as the Home Offices says 47 prisoners have been moved into designated police cells to alleviate the overcrowding crisis.
Britain's last floating prison - HMP Weare moored at Portland Harbour in Dorset - closed last year after the chief inspector of prisoners described the vessel as "unsuitable, expensive and in the wrong place".
The Home Office has refused to disclose why HMP Weare was sold to a shipbroker.
'One crisis to another'
The director of the Howard League for Penal Reform, Frances Crook, warned that plans to return to using prison ships could stoke reoffending.
Ms Crook said: "If you use ships and prison cells which are not appropriate for dealing with prisoners' needs many of them will come out and commit more crimes. So the home secretary will be responsible for more crimes.
"I want to see him supporting successful community sentences. It's not the whole answer but is a step in the right direction."
ANN WIDDECOMBE'S SUGGESTIONS
The government could commission more prison ships
They could re-open wings of prisons which had been mothballed
Disused holiday camps could be used
Army barracks could also be pressed into service
And Juliet Lyon, director of the Prison Reform Trust, said: "It seems to be just lurching from one crisis to another.
"This really feels a bit like the last straw; to have a home secretary out shopping for ships, or shoe-horning prisoners into police cells, instead of really looking at the problem."
Home Office Minister Vernon Coaker told BBC News Mr Reid was considering all options.
"What he's determined to do is to ensure we've got sufficient prison places, and obviously, he's looking at a number of ways of doing that and a prison ship is one possibility," said Mr Coaker.
Holiday camp idea
Ex-Prisons Minister Ann Widdecombe, who oversaw the commissioning of HMP Weare in 1997, told the BBC the government had seen the crisis coming "for a long time and they have failed to act".
She said she would not have decommissioned HMP Weare - and would have in fact commissioned another prison ship.
Ms Widdecombe said as well as purchasing "Portakabins from Norwegian oil rigs", the Conservative government had also considered using an empty holiday camp during her time in office.
More than 500 police cells could eventually be used
"You have the accommodation already - all you have to do is create a secure perimeter and you have a medium-security prison," she said.
Brian Caton, general secretary of the Prison Officers' Association, told the BBC that lowering the prison population was the best option.
The jail population has reached 79,714 - 65 below the all-time high of two weeks ago.
But using police cells became necessary last weekend because jails in some parts of the country have been more badly affected than others.
The Home Office spokeswoman said there was potential for 520 police cells to be used during October and November if they were needed.
But shadow home secretary David Davis said the measures would only buy the government a few weeks and would "place even more burdens on our police".
Liberal Democrat home affairs spokesman Nick Clegg said the government's position was farcical.
The government had sat on its hands for years despite warnings and was in a fix of its own making, argued Mr Clegg.