Dangerous criminals are being sent to low security open prisons to ease overcrowding, it has emerged.

Colin Moses of the Prison Officers Association feared prisoners were not "properly assessed", while the National Association of Probation Officers (Napo) said the move was "unacceptable".

Harry Fletcher, assistant general secretary of Napo, said: "I've certainly been worried for 15-18 months that individuals are being transferred into open jails who pose a risk to the public. The worry is they are not being properly assessed."

Mike Duffy, director of Scottish Prisons, admitted more 'difficult' prisoners were being put into open jails, but he denied a link between prison overcrowding and dangerous criminals being placed in low security conditions.

In a statement, Justice Secretary Jack Straw said that public safety was "paramount", adding: "All prisoners located in open conditions have been rigorously risk assessed."

The UK prison population is more than 90,000 and is said to be at an all time high.

Government statistics reveal more than 130 murderers have broken out of open jails in the last ten years.

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