THE probe into whether or not Alistair Carmichael breached the MPs’ code of conduct by approving the leak of an official memo, aimed at damaging Nicola Sturgeon, has been dropped.

Kathryn Hudson, Westminster’s standards commissioner, concluded that the matter was not within her remit.

She explained that she found that the former Scottish Secretary and his special advisor had received the memo through “official Scotland Office channels” rather than in the course of his duties as an MP and so the “allegations concerning his decision to authorise its disclosure fall outside my remit”.

At the time of the controversy – in the run-up to the May 2015 General Election – Mr Carmichael was no longer an MP as the UK Parliament had been dissolved.

The former Scottish Secretary said: "I am pleased that this is now resolved and will continue to focus on getting on with my job as MP for Orkney and Shetland."

The leaked memo between a Scottish Office official and the French consul general suggested the First Minister had told Sylvie Bermann, the French ambassador, that she would prefer David Cameron to remain in No 10 and that Ed Miliband was not up to the job as prime minister.

The alleged private sentiment was the direct opposite of what the SNP leader had been saying in public but the claim was swiftly denied by the FM; she insisted it was “100 per cent not true”. The French consul general also later said the claim was false.

When the story, dubbed “Frenchgate”, provoked a major row during the election campaign, Mr Carmichael told Channel Four News that he had only found out about the memo when a journalist contacted him about it.

However, later during a Whitehall leak inquiry he admitted he had approved the action by his spin doctor. He was forced to give up his ministerial severance pay.

At a subsequent election court hearing, brought by local constituents in a bid to oust Mr Carmichael as an MP, judges agreed that he had told a “blatant lie” in the TV interview about when he had become aware of the memo but they ruled it had not been proven beyond reasonable doubt that he had committed an “illegal practice” and so the case was thrown out.

In her report, Ms Hudson explained that, when she received a complaint about Mr Carmichael on May 29, she could only find out whether or not the matter fell within the ambit of the MPs’ code of conduct by launching an inquiry. This began on June 2.

The commissioner said that since beginning her inquiry she had “obtained evidence, which was not available to me in early June 2015, that the allegations I received relate to matters which are not within my remit”.

Parliament was dissolved for the election on March 30 last year, which meant the Lib Dem minister, along with his 649 colleagues, were no longer MPs even though they continued to receive their parliamentary salaries until May 7.

Ms Hudson explained how she had begun her inquiry last summer but, because of the election court hearing and an assessment by Police Scotland of allegations against Mr Carmichael, halted it until both these matters were concluded; by December, they had been.

The commissioner said how initially she had no evidence that a breach of the ministerial code had been considered but during the course of her inquiry was “given an assurance” it had been.

Ms Hudson, who is currently reviewing the MPs' code of conduct, said the Carmichael case might provide an opportunity to explore the boundaries between the MPs’ code and the ministerial code and whether or not candidates seeking re-election should “remain bound” by the MPs’ code during the election period.

She also noted how the code was “only part” of the system for maintaining parliamentary standards and referred to a “Westminster culture” of leaking information.

Mentioning similar references by one of the judges in the election court hearing, Ms Hudson added: “Her comments underline the culture change that would be required in order to increase public confidence in the standards system and the way in which it operates. Changes to the code of conduct and/or to the guide to the rules relating to the conduct of members are important and may assist in that process but they alone will not be sufficient.”