Ms Jamieson was challenged to stand down

The private firm handling prisoner escort services in the west of Scotland has admitted it was mainly to blame for releasing another inmate by mistake.

Nationalists called for the minister to step down and the Conservatives have questioned her handling of the issue.

But Ms Jamieson would only repeat a warning that the service must improve.

The latest incident involved the release of a man from Motherwell District Court after appearing from custody in connection with an unpaid fine.

'Error of judgement'

He should have been held to attend Hamilton Sheriff Court on a separate charge a few hours later.

Prison escort services in the west of Scotland have been awarded to Reliance Custodial Services as part of a multi-million pound contract which is due to roll out across the rest of Scotland.

But the justice minister has put the firm on notice that the process will be delayed until she is confident its performance has improved.

Reliance was appointed by the Scottish Prison Service (SPS), but the Scottish National Party's justice spokeswoman Nicola Sturgeon is demanding that Ms Jamieson step down.

I expect them to improve their performance and if they do not do that I have already made it clear that this contract will not roll out Cathy Jamieson Justice minister

Ms Sturgeon said: "I think the minister made an error of judgement in not taking the contract away from Reliance after the first monumental error and ensuring that nothing like this could happen again.

"So I think it's probably time for the minister to stand aside and allow somebody who can get a grip of the situation to do the job instead."

And the Tory justice spokeswoman Annabel Goldie accused Ms Jamieson of "running around like a banshee" between the organisations involved, after the problems emerged.

"The question has to be asked - why wasn't she doing that before the contract was placed?" she said.

Speaking after Wednesday's cabinet meeting, Ms Jamieson warned that Reliance must be seen to improve.

Reliance has been put on notice over their performance

She said: "I don't think it's acceptable that mistakes are continuing to be made.

"Reliance know that they have to improve their performance, I expect them to improve their performance and if they do not do that I have already made it clear that this contract will not roll out."

Later in parliament, Ms Sturgeon asked Presiding Officer George Reid whether he had received any request from the Scottish Executive regarding making public the contract between the SPS and Reliance.

On 21 April, Ms Jamieson had made a commitment to publish the contract "as soon as practicable".

Mr Reid said he had not been approached on the issue.