Figures for the emergency scheme, which sees criminals released up to 18 days before the end of their sentences, revealed that 3,000 of those freed had been convicted of violent crime.

It came as Justice Secretary Jack Straw announced that new projects to keep criminals out of jail will be trialled, at a cost of £14 million.

Targeted at criminals currently receiving custodial sentences of less than a year, the punishments could involve unpaid work combined with a curfew.

The Ministry of Justice's prison reform plan highlighted existing community schemes which have seen offenders trained to build bird-nesting boxes and grow vegetables.

The data for England and Wales showed 16,197 offenders were freed from the end of June - when the scheme was introduced - to the end of December.More than 300 new crimes have been committed by prisoners freed under the initiative, and 117 ordered to return to jail have gone on the run.

If the same rate of release is maintained over the next six months, it will mean 31,000 criminals will have been freed in the scheme's first year. When it was launched, ministers said the annual figure would be 25,000.

Shadow justice secretary Nick Herbert said: "Early release of offenders has put the public at risk but it has failed to deal with prison overcrowding. This policy has now created more than 300 unnecessary victims of crime.

"This early release scheme must be scrapped immediately and sufficient prison places provided so that public safety comes first."

He added that Mr Straw's reform plan was "just a rehash of prior announcements and vague aspirations".