The demand by Scottish National Party MSP Roseanna Cunningham came amid concerns two more killers will exploit a legal loophole exposed by Noel Ruddle, who was released at the beginning of August.

BBC Scotland Home Affairs Correspondent Reevel Alderson reports

On Monday, Scottish Justice Minister Jim Wallace restated a pledge to seek to change Scotland's mental health laws to stop killers gaining release from psychiatric institutions in the wake of Ruddle's release.

But SNP justice spokeswoman Ms Cunningham said she remains unconvinced the Scottish Executive will act quickly enough or that ministers are on top of the situation.

Ms Cunningham said she will call on MSPs to support a full inquiry.

Roseanna Cunningham: Serious doubts

She told BBC Radio Scotland: "It does appear as if, wittingly or unwittingly, Jim Wallace may have been giving assurances he shouldn't have been.

"The indications are beginning to look as if the legislation that was promised will be either delayed or abandoned altogether."

Ms Cunningham said that, as justice committee convenor, she is bound by the will of its members but added: "There is nevertheless an indication that a number of committee members would wish to raise the broader issues with the justice minister and may seek to do so."

The row erupted on 2 August when Noel Ruddle, who shot a neighbour dead in 1991, was released from Carstairs state psychiatric hospital.

At Lanark Sheriff Court, he successfully appealed against his detention without limit of time, arguing treatment programmes in place at Carstairs were no longer relevant to him and he could no longer be lawfully held.

Urgent review

The Scottish Executive gave assurances an urgent review of the law would be carried out.

But despite pledges from ministers that no further bids for liberation were imminent, it was revealed last week that two more killers are challenging their detention.

BBC Scotland reporter David Calder on calls for a parliamentary inquiry

Opposition parties are now stepping up their pressure on ministers in an effort to stop child killers Karl Tonner and Brian Doherty exploiting the law.

Tonner, who murdered 12-year-old Hazel Phin in 1968, is due to have his case heard at Lanark Sheriff Court later this week.

The Scottish Conservative Party's justice spokesman, Phil Gallie, said time is of the essence if the door is to remain shut.

Mr Gallie said: "The parliament gets under way next week and I want to see legislation tabled at an early date which will address the problem.

"We're told by Jim Wallace they've got to be very careful - they're concerned about the (European) Convention of Human Rights - but quite honestly I believe the protection of the public is all important.

"They should legislate first and worry about the niceties later."

Mr Wallace said every effort will be made to stop the law being exploited again.

But he stressed any new legislation would have to be capable of standing up to robust testing in the courts.

He said: "There is no backtrack on the position that I set out as recently as last week in a written parliamentary answer.

"We remain determined to try and change the law but I have never made any secret of the fact that this is by no means straightforward .