Almost 200 prisoners including murderers and sex offenders have been freed early by mistake over the past five years, according to official Government figures.
In the the past two years, the number of wrongly released inmates rose 45 per cent to a rate of almost one a week, statistics from the Ministry of Justice show.
Shadow justice secretary Dominic Grieve said: "Although the number of releases in error may be small as a proportion of all releases, they can have devastating consequences.
"As prisons have become more overcrowded, staff overworked and transfers more frequent, the number of erroneous releases has shot up.
"This is a direct consequence of Labour's incompetent mismanagement of the justice system."
Earlier this month, murder suspect Jason Bethell, 31, was accidentally freed from prison in Chelmsford, Essex.
Bethell, of Jaywick, Essex, who was on remand accused of murdering 58-year-old John Smith, later handed himself in to police.
The figures, released to the Conservatives in a series of parliamentary written answers, show 193 prisoners were let out in error between January 2005 and September this year.
A Prison Service spokeswoman said: "We take this issue very seriously and have taken action to tighten processes and focus managers' attention.
"All incidents must be reported immediately and formal investigations are required in each case.
"Prisoners released in error are normally returned to custody by the police to continue to serve their sentence.
"None of those released in error during 2009 remain unlawfully at large."
Some 32 prisoners were wrongly released in 2005, with the figure rising to 36 in 2006 and the same number in 2007.
But in the past two years the numbers have risen significantly, with 58 wrongly released prisoners last year and 30 cases between January and September this year.
The wrongly freed prisoners include Raheem Ahmed who was released from prison in Birmingham in August 2007 after serving just one week of a six-month sentence for violent affray.
And last year Terence Clegg was released from prison in Durham instead of his father, who was also called Terence Clegg and was being held at the same jail.
The father and son, from Kenton, Newcastle upon Tyne, were on remand accused of stealing from vehicles.
Three sex offenders have also been released by mistake under the End of Custody early release scheme, even though the nature of their crimes means they were ineligible.Reuse content