Over 500 prisoners, including offenders in custody for murder and other violent offences, were released early due to blunders by prison officers in England and Wales in the last 10 years, according to new figures.
A data by the UK's ministry of justice showed that in the last decade 505 prisoners have been let out of jail by mistake.
The figures obtained by the Press Association news agency through a Freedom of Information request said that 48 suspected or convicted criminals were freed by mistake in the the last year alone.
Forty-one people were wrongly released from prison and seven from court custody last year and the figure is one fewer than the previous year.
Two of those released in 2014-15 had not been returned to custody by the start of December this year, including an alleged sex offender released from court.
The data showed that criminals were released at a rate of nearly one every week due to mistakes by prison officers.
Conservative MP Philip Davies, a member of the House of Commons Justice Committee, said, "The first duty of the Prison Service should be protection of the public. These disturbing figures show that once a week the Prison Service release the wrong prisoner, and have done so for many years. This is nothing more than a shambles which puts the public unnecessarily at risk."
The UK Prison Service said public protection was its top priority.
A spokesperson said: "These incidents are very rare but we are not complacent. The number of releases in error has fallen by almost a third since 2009 and the vast majority are returned to custody very quickly."
"The Prison Service investigates each incident and they are reported to the police for further action," he said.
