The First Minister is facing demands to pay back thousands of pounds of taxpayers' money spent trying to keep the public from knowing about legal advice on Scotland's place in the EU after a vote for independence.
Labour will use debating time at the Scottish Parliament to call for a £12,000 refund one week after Deputy First Minister Nicola Sturgeon revealed there was no legal advice in the first place.
The Scottish Government went to the Court of Session arguing that the code of conduct for ministers prevents disclosure of advice, including whether advice has been sought.
Speaking before the debate, Labour business manager Paul Martin said: "This was an obscene waste of money which only heightens the farce that the SNP has created over Scotland's future in the EU. If this had really been a point of principle as Alex Salmond claimed, then they would have continued with the case.
"The reality is this was a delaying tactic as they tried to hide their dishonesty. We believe that Alex Salmond and Nicola Sturgeon should pay this money back as a gesture of goodwill to the Scottish people they have deceived at our expense."
The SNP insists that Scotland will automatically be accepted into the EU, while opponents say it would have to reapply and lose the UK's existing rights and opt-outs.
Opposition politicians said the SNP's apparent confidence on continued EU entry created the impression that advice existed. They also pointed to comments made by Mr Salmond in an interview with the BBC's Andrew Neil where the First Minister appeared to suggest he had advice on the issue.
Liberal Democrat leader Willie Rennie said Sir Peter Housden, the head of the civil service in Scotland, should explain whether he thinks money has been well spent.
As principal accounting officer for the administration, Sir Peter should be responsible for efficient spending, according to Mr Rennie.
"Sir Peter needs to explain whether it was an appropriate use of public funds to defend in court legal advice that didn't exist," he said. "The SNP say their court battle with the Information Commissioner was about a point of principle. If that's the case, why have they dropped the court case? It's clear that they went to court to avoid the embarrassing fact that they had no advice. It's an expensive way to avoid a red face for the First Minister."