Hundreds of criminals who should be in jail are on the run, including 20 murderers and nine rapists, it has emerged.
Figures released by the Ministry of Justice (MoJ) reveal that more than 100,000 offenders freed from jail over the last 10 years have been hauled back to prison for breaching their release terms.
They show the numbers being recalled have more than quadrupled in a decade.
All prisoners serving fixed jail terms since 2005 have been automatically freed when they have completed half of their sentence, regardless of the risk they pose to the public or whether they have shown any remorse.
The MoJ admitted the number of prisoners being sent back to prison had risen "significantly".
Nearly 1,000 prisoners - some of whom have been convicted of very serious crimes - have ignored the demand to return to jail and are still at large.
One offender in his 30s, who was automatically released halfway through his five-year sentence for domestic violence and threatening to kill his partner, was subject to an emergency recall after texting death threats to her within two hours of his release in Merseyside, probation union Napo said.
Another 21-year-old attacker in Surrey and Sussex, who stabbed someone he believed had informed on him, was also released halfway through a five-year sentence - only to go on the run for two weeks before being arrested close to his victim's home armed with a carving knife and crowbar.
Harry Fletcher, Napo 's assistant general secretary, said: "Thousands of those who have been released clearly pose a risk to the public.
"It is not surprising therefore that the recall rate has increased so dramatically."
Campaigners want a new system to ensure prisoners serving two years or more would only be released if they no longer posed a significant risk.
Many of those still on the run pose a clear threat to the public, Napo warned.
An MoJ spokesman said: "The time an offender spends on licence is an integral part of their sentence.
"We have robust enforcement arrangements in place to recall offenders who breach their licence conditions and present an unacceptable risk of re-offending.
"Last year over 90% of breaches by offenders under supervision were appropriately enforced by the probation service."
The MoJ figures showed that 15,004 offenders were recalled in 2009/10, compared with just 3,182 in 2000/1.
Last week, controversial changes to sentencing laws in England and Wales were shelved after David Cameron ordered a review of the proposals - which included shorter jail terms for an early guilty plea.