Government planning big new prisons
He said this would increase jail capacity to 96,000 places from around 81,500 now.
Reporting on a review of prisons by life peer Lord Carter, Straw said the government would close some older jails and build up to three large "Titan" prisons housing up to 2,500 inmates each.
"The measures I have announced ... will fulfil our commitment to provide a modernised prison system which protects the public from the most serious offenders," Straw said.
Legislation on indeterminate sentences -- blamed for adding to the overcrowding problem -- would be altered so that they could not be given for tariffs of less than two years, he added.
Under these sentences, introduced under the 2003 Criminal Justice Act, offenders are kept in jail until they are no longer deemed to be a risk to the public.
At the end of last week, jails were so full with 81,864 prisoners that 177 offenders were being held in police cells.
The government has been forced to release 11,000 prisoners early since June to cope with the lack of cells.
The prison population has been rising because sentences have grown longer, with average custodial sentences from crown courts rising to over 25 months from 20 months between 2005 and 1995.
To help ease the crowding, Straw said prisoners sentenced before new legislation came into force in April 2005 would now become eligible for automatic release under licence half way through their sentence.
At present they are only eligible for consideration for parole at that point.
As well as building new prisons, Straw said the government would convert a former Ministry of Defence site at Coltishall in Norfolk into a low-risk Category C jail.
It would also change the open side of Wealstun prison in West Yorkshire into a closed jail. Straw said the ministry was also "actively looking" at securing a prison ship.
Lord Carter's report forecasts that prison numbers will rise to nearly 95,500 by 2014 if the government takes action to limit numbers, but could hit 100,000 if no new measures are taken.
Conservative Justice Spokesman Nick Herbert said the Carter report was a "devastating indictment of 10 years of prison mismanagement."
"The government have no serious plan to reform our overcrowded jails. They have proposed greater use of weak community sentences for offenders who should be sent to jail, and they will continue to release thousands of prisoners early."
Prison reformers criticised the plans for new supersize prisons.
"Pouring money into jumbo jails will engulf any sensible plans to reform the justice system," said Juliet Lyon, Director of the Prison Reform Trust.
"Everyone knows that giant institutions don't work, whether they are schools, hospitals or prisons."













