A report last year said conditions at the prison had improved

The Scottish Prison Service (SPS) said Craiginches Prison in Aberdeen currently holds 250 prisoners, despite being built to hold 155.

An SPS spokeswoman said it hoped to build two jails in the central belt to alleviate overcrowding.

The Scottish National Party described the figure as "deeply troubling".

The SPS spokeswoman said overcrowding was a problem at all of Scotland's 16 jails.

"It is not ideal but we don't decide who goes there," she said.

These figures are shameful and they must not be allowed to continue Richard Lochhead SNP MSP

Richard Lochhead, an SNP MSP for the north east of Scotland, said: "It is an appalling situation for Craiginches to find itself in as it finds itself over capacity to record levels while at the same time it finds itself suffering from a staff shortage.

"This is clearly a situation which can not be allowed to continue and I hope the Scottish Executive will do something about this."

The MSP has written to Justice Minister Cathy Jamieson urging her to conduct an inquiry and visit the prison.

Mr Lochhead added: "I believe that a visit to the prison would be extremely useful to her and as such I have asked her to visit the prison in order to judge the conditions herself.

Inspector's report

"These figures are shameful and they must not be allowed to continue."

An executive spokesman said Ms Jamieson would be visiting all the prisons in Scotland the "next time she is in the area".

In September, a report by Scotland's chief inspector of prisons said Craiginches had gone a long way to correcting many of its faults.

Andrew McLellan's report said overcrowding, visiting arrangements and long-term prisoners' needs still required attention.

But he praised staff for working in difficult conditions and trying to find activities for inmates.