Scotland will need another new jail to cope with the increase in prisoners which will result from new legislation which is going through parliament.

Ministers yesterday acknowledged they will have to reverse the Scottish Executive decision in 2002 to restrict the prisons expansion to two new jails, in the face of sentencing reforms.

Cathy Jamieson, the Justice Minister, yesterday admitted that Scotland will need to expand its prison estate to cope with the additional 2200 prisoners predicted under new legislation.

Last year, the Scots prison population reached 7320. The average daily figure is expected to increase to 8200 by 2015-16 and if justice policies change it could hit 9500.

The Custodial Sentences and Weapons (Scotland) Bill, which would bring an end to automatic early release, will require more than £67m in funding, according to the financial memorandum. It could also result in Scotland taking the lead in western Europe for having the highest prisoner population for its size.

Ms Jamieson said in order to cut reoffending rates in the long term, in the short term the prison estate would have to expand.

She admitted the legislation comes with implications and a price tag. However, she stressed the current system of automatic and unconditional early release requires wholesale reform.

"There is the potential for looking imaginatively at the sites we have got but we also have to face up to the fact that there may well be the need for additional facilities," said Ms Jamieson.

"We may have to take on that short-term pain. If we need to provide additional places in the short term, it is not just about the places but the programmes and regimes which go with that.

"If we're serious about reducing reoffending, if we want to decrease our prison population, if we want to stop that revolving door, we need to do something about the whole system."

In 2002, Jim Wallace, the former Justice Minister, agreed to create two new prisons, at least one of which would be private, but ruled out plans for a third prison, saying instead that efforts would be made to boost the use by courts of alternatives, such as community service orders.

Last month, The Herald revealed that ministers had given the go-ahead for a controversial 700-cell prison at Low Moss in Bishopbriggs, overturning a refusal by the local authority.

The executive has also agreed to a private 700-cell prison being built at Addiewell, West Lothian.

The proposals in the Custodial Sentences and Weapons (Scotland) Bill could now see a third prison being created.

If passed, the legislation will result in all those sentenced to more than 14 days in prison serving at least part of it under licence in the community. Currently, criminals sentenced to up to four years behind bars are freed after serving half their jail term, often without supervision.

In principle, the legislation has been universally welcomed. However, most of the evidence put to the justice committee warns that it is unworkable.

Ms Jamieson said she has established an implementation group to work through concerns raised. She also indicated that even without changes to the sentencing system, prison numbers could continue to rise because of improved crime clear-up rates.

She argued the new legislation could cut reoffending in the longer term, as criminals would be given support during the community part of their sentence in a bid to tackle the causes of their offending behaviour.