SCOTLAND'S sex offender prison is to be emptied and its most dangerous criminals dispersed as part of plans to modernise the country's jails.

Some 150 sex offenders are to be moved from Peterhead prison to Glenochil where they will have to be segregated from mainstream inmates.

Peterhead, which has held and tried to treat Scotland's most dangerous sex offenders, will take mainstream prisoners in the short term in the run-up to the opening of the new community prison HMP Grampian.

The move comes despite concerns raised by Brigadier Hugh Monro, HM Chief Inspector of Prisons, last week about overcrowding in Glenochil.

The prison service said space is being created in Glenochil to accommodate sex offenders and overcrowding has been reduced.

Once infamous for riots, Peterhead was transformed into a centre of excellence dealing with sex offenders.

When it was earmarked for closure in 2002, Alex Salmond, the then SNP MP for Banff and Buchan said it would be a "disaster" to shut the jail, which he described as "the jewel in the crown of the prison service".

At that stage it housed almost 300 inmates, the majority convicted sex offenders.

There were calls for the jail to be closed after a spate of riots in the late 1980s, but the community argued it was one of the few major employers in the area.

Following consultation, the SPS announced in 2009 the prison would close and be replaced with HMP Grampian in 2014.

Brigadier Monro revealed sex offenders recently moved to Glenochil as part of the changes have been complaining, as they are unhappy about sharing cells.

He said the problem has been caused by overcrowding due to prisoners being transferred from another prison – and hinted the situation could get worse.

Brigadier Monro said there has been "a disproportionate number of complaints" from prisoners having to double up in the segregated sex offenders' wing of Glenochil Prison, in Clackmannanshire.

He said "fair progress" had been made since the last full inspection in 2010, but added the impact of a transfer of 150 sex offenders from Peterhead to Glenochil's Harviestoun Hall had been "considerable".

He said: "Overcrowding has become more acute since my last visit. The arrival of sex offenders from Peterhead has complicated the situation and needs to be addressed in light of the further tranche due to transfer from Peterhead in the near future.

"Strict separation requirements complicate the regime, causing restrictions of access to activities and facilities."

A spokesman for the SPS said overcrowding in Glenochil has been reduced. He said: "We are currently in the process of arranging the transfer of the remaining prisoners from Peterhead to Glenochil. We have been freeing up space at Glenochil to accommodate these moves. This has been made possible by the recent opening of Low Moss.

"When we have transferred the prisoners we will backfill with mainstream prisoners from Aberdeen to give staff experience with dealing with the mainstream in anticipation of the opening of HMP Grampian."