An independent monitoring board has slammed Surrey Police’s “unacceptable” handling of allegations of sexual assault made by inmates at a women’s prison.

The annual report released by the Independent Monitoring Board (IMB) also criticised what it described as the “lack of desire” by Surrey Police to finish investigations on two sexual assaults at Downview Prison, in Banstead, one involving a prison officer and an inmate and the other involving two inmates.

But Surrey Police has defended its approach and said it was disappointed the board did not consult it to get an accurate picture of what has happened.

The report, drawn up by a group of members of the community appointed by the Secretary of State for Justice, praised the prison for providing a safe and caring environment with no deaths in custody and a low rate of self-harm compared to other prisons.

It also praised its full employment programme and the work it does to provide release employment opportunities.

But it concluded that an intrusive target-driven approach and a lack or resources and manpower is preventing the governors from managing the prison in the most effective way.

Other issues raised by the IMB included statements from staff and prisoners saying the prison is “awash with drugs” even though they found difficult to verify the information, the halving of the Offender Management staff and the substantial number of officers on sick leave.

On the issue of investigating alleged sexual assaults at the prison the IMB report said: “Police investigations into allegations by prisoners of sexual assaults have dragged on for too long, causing unacceptable stress on staff and prisoners alike.

"The Surrey Police seem to show no desire to close the two serious allegations to which we refer.”

It also accused Surrey Police of “putting little urgency into incidents in prisons” and urged the Home Office to advise constabularies that “serious prison inquiries should be treated no differently from normal police investigations.”

A spokeswoman for Surrey Police said: "Surrey Police treats all allegations of sexual assaults extremely seriously wherever they occur.

“The suggestion that a time limit can be applied to such investigations is completely unrealistic as every enquiry is different.

"Surrey Police works hard to meet the needs of every victim of these offences and has invested significantly in a specialist unit to support these victims, be they in prison or elsewhere.

“Both of the investigations which appear to be referred to in the Independent Monitoring Board report were concluded within three months and were finalised before the publication of the IMB report.

"Surrey Police has received no complaints or adverse comment from any individual in relation to these investigations.

“We are disappointed that we do not appear to have been contacted by the Independent Monitoring Board in relation to their concerns to ensure the accuracy of their information."