Former Liberal Democrat minister Alistair Carmichael is facing a formal sleaze probe over the leaking of a memo intended to damage SNP leader Nicola Sturgeon.
Parliamentary standards commissioner Kathryn Hudson has launched an investigation into whether the Orkney and Shetland MP broke the Commons Code of Conduct.
Following a cabinet office leak inquiry, the ex-Scottish secretary admitted last month that he allowed his special adviser to release a record of a private conversation in which Ms Sturgeon allegedly said she wanted David Cameron to remain Prime Minister.
The commissioner’s office said her investigation is focused on Paragraphs 10, 14 and 16 of the Code of Conduct.
Paragraph 10 states that members should “base their conduct on a consideration of the public interest, avoid conflict between personal interest and the public interest and resolve any conflict between the two, at once, and in favour of the public interest”.
Paragraph 14 requires that “information which Members receive in confidence in the course of their parliamentary duties should be used only in connection with those duties. Such information must never be used for the purpose of financial gain”.
Paragraph 16 warns MPs not to “undertake any action which would cause significant damage to the reputation and integrity of the House of Commons as a whole, or of its Members generally”.
There had been speculation that the commissioner might not be able to take the investigation on because the memo emerged during the election campaign – when Mr Carmichael had ceased to be an MP.
However, his special adviser Euan Roddin told the Cabinet Office leak inquiry that he provided the memo to the Daily Telegraph on April 1 – raising the possibility that discussions had taken place beforehand when Mr Carmichael was still a member.
A Lib Dem spokesman said: “Alistair has always been clear that he would co-operate with any investigation that was undertaken. That remains the case. He will co-operate in full with the standards commissioner’s investigation.”
The Commons Code of Conduct says it “applies to Members in all aspects of their public life”.
The standards commissioner’s office refused to confirm whether she was looking at behaviour that took place before the start of the “short” election campaign on March 30 – at which point Mr Carmichael officially stopped being an MP.
Mr Carmichael was one of just eight Lib Dem survivors on May 7 but his majority of more than 10,000 was squeezed to 817 votes by the SNP.
He has said he would have resigned over the memo, which appeared in the Daily Telegraph on April 3, if he was still a government minister and has declined his ministerial severance payment. The document, written by a civil servant, wrongly claimed Ms Sturgeon told French ambassador Sylvie Bermann that she would prefer to see the Conservatives remain in power.
Police Scotland has received a complaint about Mr Carmichael’s actions, and a petition has been lodged at the Court of Session in Edinburgh in an effort to have his election overturned.