Alistair Carmichael
Alistair Carmichael admitted giving permission for the memo to be leaked to the Daily Telegraph prior to the electionGetty

Lib Dem MP Alistair Carmichael will not face legal action after admitting leaking a memo claiming SNP leader Nicola Sturgeon would prefer the Conservatives to win the 2015 general election. The former Scottish secretary admitted it was an "error of judgement" to leak a document that said Sturgeon would rather back David Cameron over Ed Miliband during a conversation with Sylvie Bermann, the French ambassador, in February.

The MP for Orkney and Shetland previously denied having anything to do with the memo, which was first published in the Daily Telegraph, then admitted he gave permission to his then special adviser Euan Roddin to release the memo. Sturgeon denied the claims as "100% untrue" and accused Whitehall of "dirty tricks" following the release of the memo.

Four constituents had tried to challenge the election of Carmichael under the Representation of the People Act 1983, claiming he misled voters over the incident. The case has been dismissed after judges ruled that it cannot be proven beyond all reasonable doubt that he had committed an illegal practice. The ruling means there will not be a by-election in Orkney and Shetland and Carmichael will remain the last surviving Lib Dem MP in Scotland.

Election Court judges Lady Paton and Lord Matthews ruled that Carmichael had told a "blatant lie" when he told Channel 4 News he only become aware of the memo when contacted by a journalist

Paton said: "There is no dispute that the words 'I told you the first I became aware of this, and this is already on public record, was when I received a phone call on Friday afternoon [3 April 2015] from a journalist making me aware of it' constituted a false statement of fact, in other words, a lie. Obviously the first respondent had been aware of the existence of the memo and its contents as described to him by Mr Roddin since the flight to the Faroe Islands in March 2015. Moreover he had authorised Mr Roddin to release the memo to the Daily Telegraph."

However, on the matter of whether the lie could properly be characterised as a false statement of fact "in relation to [his] personal character or conduct", the judges were left with a reasonable doubt. Paton said: "In the present case, when speaking to the Channel 4 interviewer, the first respondent did not make such an express statement about his personal character or conduct. We are not persuaded that the false statement proved to have been made was in relation to anything other than the first respondent's awareness (or lack of awareness) of a political machination."

Carmichael said he is pleased with the outcome and the whole case was "politically motivated". He added: "It was a deliberate attempt by nationalists to remove the last Scottish Liberal voice at Westminster, and is a mark of the unhealthy polarisation of Scottish politics since the referendum. I shall continue to represent Orkney and Shetland as a Member of Parliament to the best of my ability, as I have done for the past 14 years."