SCOTLAND'S most senior law officer, the Lord Advocate, has been drawn into the row over Alex Salmond's claims about legal advice on an independent Scotland's membership of the EU.

Frank Mulholland has been challenged to explain his role in drawing up three key documents outlining the Government's claim that EU membership would be automatic if Scotland split from the UK.

In a letter yesterday, Labour's external relations spokeswoman Patricia Ferguson asked the QC whether he or Solicitor General Lesley Thomson had seen or commented on the documents prior to publication.

The move follows Mr Salmond's claim in a TV interview in March that the two law officers had been consulted on EU membership "in terms of the debate".

The First Minister has faced claims he lied during the interview since it emerged last Tuesday that specific advice on the EU had not been sought from the law officers at that time.

He has denied the claim, but agreed to an inquiry into allegations he broke ministerial rules banning him from revealing the existence of legal advice.

Ms Ferguson also called on the Lord Advocate to make an emergency statement to Parliament.

She said: "We have seen a number of contradictory statements from Alex Salmond and Nicola Sturgeon this week, and they have failed to give a credible explanation for the chain of events surrounding this crisis.

"We would like to afford the Lord Advocate an opportunity to make a statement or give evidence as a way of restoring confidence in this process. He should have nothing to hide and it is time he stepped up.

"Scotland's membership of the European Union and our currency are fundamental questions about our future, but the people of Scotland no longer trust this SNP Government to be clear about the consequences of breaking up the United Kingdom."

The Government has claimed an independent Scotland would continue as an EU member on the same terms as the UK – including its euro currency opt-out – in three key documents, Choosing Scotland's Future, published in 2007, Your Scotland, Your Voice, in 2009, and Your Scotland, Your Referendum, in January this year.

The documents were "underpinned by legal advice from the law officers", the First Minister's chief spin doctor said.

However, the position has been contradicted by the President of the EC, Jose Manuel Barroso, and by Spain's Foreign Minister, Jose Garcia-Margallo.

The row over legal advice has plunged Mr Salmond's Government into its deepest crisis since he came to power in 2007. It erupted last Tuesday when Ms Sturgeon announced the law officers would be consulted on an independent Scotland's membership of the EU in the wake of the Edinburgh Agreement paving the way for the referendum.

The LibDems and Tories also stepped up pressure on Mr Salmond. Michael Moore, the Scottish Secretary, said he would use a speech to the LibDem conference in Dunfermline today to accuse the SNP "playing fast and loose with Scotland's future to meet their own narrow ends".

And in a speech to activists yesterday, Scots Tory deputy leader Jackson Carlaw claimed trust in the Government had been damaged.

A Crown Office spokesman said the Lord Advocate had not received Labour's letter, but would respond in due course.

The Scottish Government declined to comment, but SNP MSP Jamie Hepburn said: "Labour should remember that the law officers of Scotland are entirely independent of party politics and are not there to be used for party political point-scoring."