Labour have said the ministerial code is "not fit for purpose" as an investigation is to take place to decide if Alex Salmond broke it with his stance on legal advice over an independent Scotland's future in Europe.
The First Minister announced this week that he had referred the matter to the independent panel of advisers on the Scottish Ministerial Code.
A furious row erupted after Deputy First Minister Nicola Sturgeon revealed the SNP administration had only recently commissioned specific legal advice on the issue, when Mr Salmond appeared to suggest such advice had been taken in an earlier television interview with the BBC's Andrew Neil.
MEP Catherine Stihler had previously submitted a Freedom of Information request to try to ascertain what legal advice, if any, had been given to the Scottish Government.
Ministers took the case to the Court of Session to try to prevent the release of any information.
Two former lord advocates - the Rt Hon Lord Fraser of Carmyllie QC and the Rt Hon Dame Elish Angiolini QC - and Sir David Bell, a former permanent secretary in the UK Government's education department, will investigate if the First Minister broke the code on the issue.
But Lewis Macdonald, Labour's justice spokesman, wants to see an independent judge review the way the ministerial code operates.
He said: "The ministerial code is being used by the First Minister as his get out of jail free card.
"Instead of being used as a way of keeping the ministers honest, he is using it as a defence as he bends and tries to get round the rules. It's not fit for purpose.
"The truth is Alex Salmond effectively writes the code, signs it off and then decides who will police it.