LABOUR is pushing the Lord Advocate to make a statement to parliament to explain a hold-up in the case involving Michelle Thomson's property deals - despite legal sources insisting that an investigation was ordered days after finding out the MP was involved.

It has emerged that the Law Society of Scotland raised the case of the Edinburgh West MP's solicitor, Christopher Hales, who was struck off for professional misconduct for his part in 13 deals closely linked to Ms Thomson which potentially involved mortgage fraud, with the Crown Office on three occasions before it ordered an investigation into "alleged irregularities".

However, it is understood that Ms Thomson's name was not mentioned in the first two briefings when the case was discussed informally, in December last year and at the height of the general election campaign in April. Insiders have said that it was only when the full report was received in July that they became aware of the names of the Mr Hales' clients.

Scottish Labour called for the Lord Advocate, Frank Mulholland, QC, to make a statement on the floor of Holyrood saying there remained major unanswered questions over the case.

Jackie Baillie, the party's public services spokeswoman, said: "After First Minister’s Questions and the Law Society press conference it's clear there remain major unanswered questions about who knew what and when about Michelle Thomson's property deals.

"Nothing less than full transparency will do in this case, but the more we learn, the more questions we have. The Scottish public has a right to know about the handling of the case, with the Crown Office being informed in December 2014, April 2015 and again in July 2015. Why did it need three separate communications to kick off an investigation?

"That is why we need a full statement to Scottish Parliament from the Lord Advocate. At the heart of this story are vulnerable families losing out for the financial gain of others. There is a perception that the establishment is closing ranks to protect one of their own. It is therefore essential that we have a robust justice system which is transparent and operates without fear or favour."

The Crown Office issued a curt response to the statement, with a spokesman saying: "The Crown Office has repeatedly made its position on this matter clear."

Ms Thomson, who built a property portfolio by at times purchasing homes from people in financial distress, denies any wrongdoing and had pledged to return to frontline politics.

She held a surgery in her constituency yesterday and posted a photograph on Twitter of her in front of the Forth Road Bridge alongside the message: "Cracking morning to be out & about in constituency."

Meanwhile, the SNP has warned its MPs to come clean to party HQ over any skeletons in their closets, after Nicola Sturgeon insisted that her party was not aware of allegations surrounding Ms Thomson until they came to light in the press.

The party made her spokeswoman for the high-profile business, innovation and skills portfolio at Westminster, before she left the party whip on Tuesday meaning she will sit in the Commons as an independent and is suspended from the party. The First Minister has hinted that her party's vetting procedures will be tightened up in light of the scandal.

An SNP spokesman said: "All elected representatives have an ongoing obligation to notify the party of any matter which may be relevant and may have arisen since their original assessment."

When asked on Wednesday whether the Lord Advocate would make a statement to parliament, the First Minister said: "The Lord Advocate when it comes to investigation and prosecution of crime is entirely independent of ministers and it would be inappropriate for me as First Minister to encroach on what are his independent responsibilities."