A court has been asked to dismiss a legal challenge to the election of former Scottish Secretary Alistair Carmichael.

Four of the Liberal Democrat MP's Orkney and Shetland constituents have raised a case at the Court of Session in Edinburgh, claiming he misled voters during the general election campaign over the leaking of a memo about First Minister Nicola Sturgeon's meeting with a French ambassador.

As the full hearing got under way today, Mr Carmichael's lawyer told the court the petition lodged in a bid to oust him should be dismissed as it is "irrelevant" and "bound to fail".

Mr Carmichael, Scotland's only Liberal Democrat MP, was not present in court for the first day of the hearing.

The hearing, at a specially-convened Election Court, began with judge Lady Paton saying it would focus on legal debate surrounding Section 106 of the Representation of the People Act 1983.

It makes it a criminal offence to release a "false statement" about the character and conduct of an election candidate.

Lady Paton said the only people entitled to address the court were the lawyers for both sides and stressed that anybody who interrupted proceedings would have to leave the court.

Opening the legal debate, Roddy Dunlop QC, representing Mr Carmichael, asked the court to "dismiss the petition as irrelevant" and added that it is "bound to fail" in law.

The former Scottish secretary came under pressure to quit as an MP after admitting responsibility for a leaked memo written by a civil servant which wrongly suggested Ms Sturgeon wanted David Cameron to win the general election.

Cabinet Secretary Sir Jeremy Heywood ordered an inquiry after the memo, which claimed Ms Sturgeon told French ambassador Sylvie Bermann that she would prefer to see the Conservatives remain in power, became public.

Following the investigation, Mr Carmichael, who had previously insisted he was unaware of the memo, admitted he had allowed his special adviser Euan Roddin to release details of the document which appeared in the Daily Telegraph on April 3.

Mr Dunlop today said it was accepted that Mr Carmichael's claim in a Channel 4 interview that he had no prior knowledge of the leak was "not correct".

The QC also called for a strict interpretation of the Representation of the People Act on the grounds of the "extreme results" that would flow from being found in breach. These include disqualification from standing for election and not being allowed to vote for three years, the court heard.

The legal challenge - funded via a crowd-funding appeal - is being broadcast live in what is believed to be a television first for a court hearing in Scotland.

The Election Court could sit for two days to hear the case, which is thought to be the first election petition brought in Scotland since 1965.

It is being heard by two judges, Lady Paton and Lord Matthews.

Mr Dunlop insisted the petitioners are attempting to redefine a section of the Act designed to prevent the traducing of another candidate's private character to encompass common political sparring.

He asked to court to distinguish between public or political statements, such as a candidate's political preferences, between statements which relate to their private character such as allegations of corruption.

He also said there are no provisions in the Act to incriminate "self talking", in this case making a false statement about knowledge or otherwise of a leaked memo.

"If my learned friend (counsel for the petitioners) is right then this court might expect to get a lot busier," he said.

"I ask the court to pause and consider the precendent that they are being asked to set, because the combination of 'self talking' and 'falsity equals private' is that henceforth any prospective MP will in the run up to an election effectively be strapped to a lie detector and administered a truth serum.

"That is because any untruth, no matter how public the subject, would engage section 106 (of the Act).

"You might say: 'What's wrong with that, what's wrong with expecting honesty from our politicians?'

"The answer is that for 120 years it has been thought appropriate by parliament to distinguish between the public or political on the one hand and the private on the other.

"If there is to be an elision of that distinction that is a matter for parliament, and we must not forget the basic premise of separation of powers.

"The 1983 Act is a limited derogation of powers from the default position whereby the conduct of MPs is regulated by Parliament, and this court as a creature of statute should not arrogate to itself powers which parliament did not intend to provide."

He suggested that the approach of the petitioners would limit the "cut and thrust of politics".

"One cannot emasculate that process by creating a situation where every syllable is guarded," he said.

"The statutory provisions were introduced, for clear and good reason, to prevent the traducing of private character for political gain.

"They were not introduced to allow disappointed electors to pour over every utterance of an opponent in an attempt to unseat him."

Jonathan Mitchell QC, representing the petitioners seeking to oust Mr Carmichael, later set out their stance.

They maintain that the Lib Dem MP - who was ultimately re-elected with a majority of 817 - acted in the way he did "to affect his own return (as a constituency MP) and by obvious logic the return of any other candidate in Orkney and Shetland," Mr Mitchell told the court.

It was "reasonable" for the petitioners to make such an inference, he added.

The QC said Mr Carmichael does not dispute that he made certain statements of fact which were false before or during an election.

But he went on: "He (Mr Carmichael) does dispute that this was for the purpose ... of affecting the return of a candidate at the election."

In the petition lodged with the court, the four constituents claim the fact that Mr Carmichael "saw fit to ... deliberately conceal his role in the leak of the memorandum, relates directly to his personal character".

It goes on: "It calls into question his integrity as an individual. It thus calls into question his suitability to represent the constituency at Westminster."

The paperwork calls on the court to "determine that Alistair Carmichael MP was not duly elected or returned and that the election was void".

The hearing continues on Tuesday.