A Derbyshire MP has demanded an inquiry into the number of inmates who have absconded from Sudbury Open Prison.
More than 660 Sudbury inmates have absconded in 10 years
Patrick McLoughlin, Conservative MP for West Derbyshire, said he had written to Home Secretary John Reid about the situation at the prison.
Five convicted killers have absconded from the jail since November.
Mr Reid said the number of prisoners absconding from Sudbury had fallen and escape rates at open jails in England and Wales were at a 10-year low.
Mr McLoughlin said: "I have asked him to have an inquiry because we're talking about five people that have been convicted of the most serious crime that you can be convicted of."
Mr Reid said on Friday: "It is the nature of open prisons that there is a risk of people walking out."
However, he acknowledged that any missing prisoner was an "important and serious case".
Duncan MacNeil, 41, and Paul Michael Neale, 50, were reported missing from the jail on Wednesday.
MacNeil from London was jailed for life in 1982. Neale was sentenced to life imprisonment in Bristol in 1983 for a murder in Wiltshire.