Nearly 100 murders have been committed by offenders on probation in the past two years, Home Office figures show.
John Monckton was stabbed to death by an offender out on parole
There were 60 murders by criminals out on licence in 2004-05 and 38 in the following 12 months.
In comparison, there were 24 murders in 2000, and 29 in 2003. There were also 106 rapes during 2004-05 compared with 18 in 1999.
There were 614 convictions for further serious offences committed by criminals on licence during the two year period.
The figures come after a series of high-profile cases in which offenders have committed serious crimes, including murder, while on parole.
City banker John Monckton was stabbed to death at his family home in Chelsea in November 2004.
His killer, 25-year-old Damien Hanson, had been out of prison for only three months after being released halfway through a 12-year sentence for attempted murder.
The figures also show the number of years spent in prison by criminals serving a mandatory life sentence remained stable at 14 years before parole.
But it revealed that for those serving other life sentences, such as discretionary life terms, the average time served fell by three years.
Shadow home secretary David Davis said the new data was a "shocking indictment of government failure across the board to protect the public".
"How much longer must the public pay the often lethal price of this failure?
"The government should answer our call to provide sufficient prison places so that those offenders who should be in prison are," he said.
But Harry Fletcher, assistant general secretary of the probation union Napo, said the figures were "not surprising".
"Serious offences have always been committed by people on parole or on probation and this is not surprising given their previous convictions and backgrounds."
Mr Fletcher said the rise in offences committed by people on parole could be due to an increase in the number of people released early from prison.
"The government must ensure that the Probation Service is fully resourced in order to minimise the chances of serious re-offending in the future," he said.