Dorchester Prison is struggling to provide a positive and challenging environment for inmates because of overcrowding, government inspectors said today.

HM Chief Inspector of Prisons Anne Owers also raises concerns about the prison's ability to cope with mentally ill prisoners in a report out today and a lack of privacy in the cells.

But Ms Owers praises the prison for its good staff and prisoner relationships, and the relationship the prison has with the local Primary Care Trust. She said the prisoners also felt safe in the prison on their arrival and throughout their stay.

The comments follow an announced inspection of the Victorian jail by HM Inspectorate of Prisons in April this year.

She said: "Dorchester is a small, old local prison. It holds nearly twice as many prisoners as its certified normal accommodation, many in cramped cells with unscreened toilets.

"It has the advantage of holding prisoners who are mainly local to the area but it has the disadvantage that it is not able to offer them sufficient purposeful activity."

"Dorchester is a small example of a much greater problem. It is genuinely a local prison largely receiving men from neighbouring areas.

"It enjoys good staff-prisoner relationships, with mutual respect on both sides. It could therefore be a community prison, working with prisoners and the community to provide skills and support to reduce re-offending.

"We saw some evidence that this was developing, particularly in the resettlement work. But like many overcrowded local prisons, Dorchester is not yet able to provide the positive and challenging environment that its prisoners need if they are not to continue to return." said Ms Owers.

Jerry Petherick, south west area manager for the prison service, said he believed conditions at Dorchester were improving and that the report was an improvement on the last inspection, which took place in 1999.

"We have come a long way but there is still a long way to go. The establishment is doing all it can to improve conditions. It is being well led and well managed."

Steve Holland, governor at the North Square prison, said that following the inspection an action plan has been drawn up and was already being implemented.

"One of the main criticisms is a lack of privacy in cells. We have toilets in cells designed for one person with two people in the cells, which isn't on but we have been struggling to provide the right privacy screens but it's more than just putting up."

And he said that a new activity and resettlement unit, which is due to open shortly would help improve the quality of out of cell activity offered to prisoners.

He said more was being done to ensure that once prisoners leave jail they do not reoffend.

"It does take some time to implement but everyone is starting to talk the talk and things are improving," said Mr Holland.

Peter Gregson, chairman of the prison's Independent Monitoring Board, said he believed that everyone was working together to make Dorchester Prison better.

"Prisons are horrible places and there's no question that things need to be improved over time but everyone has been pushing in the right direction to achieve those improvements.

"The important thing is that Dorchester is a safe prison for both staff and prisoners."