The parliamentary watchdog will not investigate a complaint made against MP Michelle Thomson, who has stepped down as  SNP party whip at Westminster amid an investigation into her property dealings.

The Parliamentary Commissioner for Standards has confirmed she will not be investigating a complaint about Ms Thomson raised by former Lib Dem MP John Barrett.

A decision has yet to be made on whether to take forward a separate complaint by Conservative MP Andrew Bridgen.

It came as it emerged that police were alerted to concerns about the solicitor under investigation over property deals linked to Ms Thomson as long ago as 2011.

The Law Society of Scotland confirmed it submitted a suspicious activity report (SAR) on Christopher Hales to the Serious and Organised Crime Agency (SOCA).

The move followed an inspection of Mr Hales' firm which eventually led to him being struck off as a solicitor in 2014.

MSPs said the report to SOCA, which now operates as the National Crime Agency, underlined the need for the Law Society to publish all its documents on Mr Hales.

The call was first made during First Minister's Questions on Thursday and backed by Nicola Sturgeon.

However, the Law Society said it would be "irresponsible" to release its files as disclosure could prejudice possible future legal proceedings.

Mr Hales was involved in a number of property deals on behalf of Ms Thomson.

Some involved buying property at a knockdown price from people in financial difficulty before selling on at profit, on the same day, in return for a "cashback" payment from the buyer.

Such "back to back" transactions have been linked to mortgage fraud.

Ms Thomson, who had been the SNP's business spokeswoman in the House of Commons, denies any wrongdoing or illegal activity and has offered to help police with their inquiries.

She has resigned the party whip until the investigation into the property deals is concluded.

The Law Society has come under scrutiny over the length of time taken to formally submit evidence on the case to the Crown Office.

Although concerns about potential criminal matters were brought to prosecutors in December 2014 and April 2015, they were not formally raised until July 2015.

In a statement, the Law Society said it was fulfilling a legal duty by submitting a SAR to police.

The National Crime Agency, said it could neither confirm or deny receiving the SAR, as it does not comment on individual cases.

SARs alert law enforcement agencies to potential money laundering.

The UK Financial Intelligence Unit (UKFIU) identifies the most sensitive SARs and sends them to the appropriate organisations for investigation.

The remainder are made available to UK law enforcement bodies via a secure channel.

Scottish Conservative MSP Murdo Fraser said: "This is an astonishing development which raises a new raft of questions.

"Both the First Minister and the Lord Advocate have said in the Scottish Parliament that they knew nothing of this.

"Yet here we see that the Law Society flagged this up in 2011 - what has been happening for the last four years?"

Scottish Labour's Jackie Baillie said: "We need full disclosure from all of the agencies and organisations involved.

"When did Michelle Thomson know that this case had been reported to a law enforcement agency and when did she disclose this to anybody during the referendum and general election campaign?

"These latest revelations only strengthen the case for an independent external inquiry into the Law Society's role in this case and for the Law Society to publish all papers on this matter.

"Without credible answers, the public will get the impression that the Scottish establishment is closing ranks to protect one of its own."