No patients will be moved from Scotland's top security hospital without ministerial approval, First Minister Alex Salmond pledged yesterday.

The announcement follows the revelation in The Herald yesterday that almost half the patients at the State Hospital at Carstairs, including several killers, are to be transferred to lower security units.

Andreana Adamson, chief executive of the State Hospital, told The Herald that the number of beds at the institution are to be cut from 240 to 140 by 2011.

The move will see male patients not requiring the high security at the hospital moved to medium secure units where they will be subject to less strict rules, and eventually allowed out on their own.

Labour's health spokeswoman Margaret Curran demanded an assurance that money will be be available to ensure public safety is not "compromised" as a result of the changes.

Speaking during First Minister's Questions at Holyrood, she asked: "Can I ask you if you appreciate that the public interest in this will be substantial, and therefore do you agree with me that it is appropriate that the health secretary make a statement to parliament confirming that appropriate measures are in place?"

Mr Salmond told MSPs: "Any transfer of a restricted prisoner and resident at Carstairs requires ministerial approval. That is the guarantee of public safety that we have." The SNP leader pointed out that the current process began under the previous Labour/LibDem administration.

He went on to say: "And you can be absolutely certain that public safety will be paramount in all of these decisions."

The State Hospital at Carstairs is Scotland's only high-security hospital.

It provides assessment and care in high-security conditions for people with mental disorder who, because of the danger they pose to the public, cannot be cared for in other institutions.

The move revealed yesterday comes amid fears patients kept in an "excessive" level of security could sue the government under the European Convention on Human Rights.

It is also in line with new national mental health policy to provide appropriate local services.

"In the light of prospective changes at Carstairs it is vital that the public are given firm assurances about the safety and security issues," said Mrs Curran.

Bill Aitken, the Tory justice spokesman, also raised concerns.

"Having visited Carstairs and indeed met with a number of patients I accept that they are more to be pitied than blamed but they do present a real hazard in some instances. I hope the security at these other two units will be sufficient to provide the reassurance required."

"The SNP Government need to be aware of public anxiety on this issue and take clear and firm steps to make sure this process of change is transparent and that measures are in place to make sure there is no risk to the public.

"I am calling on Nicola Sturgeon to make it clear to the parliament what actions she is taking to make sure the safety of the public is paramount and the needs of the patients are addressed."

Mr Salmond also said he would "look closely" at a new scheme south of the border allowing parents to ask police if individuals have convictions for paedophile offences.

The scheme to be trialled in four areas - Cambridgeshire, Hampshire, Cleveland and Warwickshire - will give parents new powers to check the status of people given regular unsupervised access to their children. Mr Salmond told Labour's Paul Martin during First Minister's Questions that the administration would be monitoring it.

"We will be looking very closely at what is a pilot scheme south of the border to see if it has lessons for us," he said.

The pilot was announced by Jacqui Smith, the Home Secretary, last weekend and will allow single mothers to ask police whether potential boyfriends have child sex convictions before they start a relationship.

Family members or neighbours who regularly look after children could also be checked.

Mr Salmond, though, said that the Scottish Government is taking "substantial steps" to deal with the issue.