ALISTAIR Carmichael has described the past week as ‘the worst five days of my life’ – and next week may not be any better as the ‘Frenchgate’ affair escalates.

Campaigners trying to oust the embattled Orkney and Shetland MP have launched a legal challenge at Scotland's highest civil court.

They have lodged a petition at the Court of Session in Edinburgh in a bid to have the former Scottish secretary's election overturned. It is understood to be the first such case to come before the Scottish courts in 50 years.

Carmichael has been under severe pressure to quit after admitting responsibility for a leaked memo which wrongly suggested that First Minister Nicola Sturgeon wanted David Cameron to win the general election.

A crowd-funding appeal to raise money for a legal bid to have Carmichael's result overturned had raised more than £44,000 last night - over 73 per cent of its £60,000 target.

The campaign - The People Versus Carmichael - was set up by Orkney residents Fiona MacInnes and Tim Morrison.

He was at the Court of Session where the petition was formally presented by Jonathan Mitchell QC at a hearing before Lord Uist. The judge made an order for Carmichael to be formally notified of the petition.

Speaking outside the court, Robert Holland, partner at solicitors Balfour and Manson, said: "An election petition has been lodged today at the Court of Session.

"It has been accepted by the court and warrant has been granted for service.

"As far as the legal proceedings go it will take its usual course."

Morrison said: "I'm a voter from Stromness in Orkney and one of the four petitioners asking the Court of Session to request the result of the general election in our constituency to be examined.

"Everyone has an opinion on what happened and what Mr Carmichael has done or not done, but we ordinary voters want to have our say now that we are in full possession of the facts."

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

Carmichael apologised after the Cabinet Office investigation into the leak concluded he ''could and should have stopped the sharing of the memo''.

Morrison added: "Mr Carmichael has apologised to us, his constituents. It's up to us to forgive him if we choose to in the ballot box.

"This should happen as soon as possible and certainly not in five years.

"Today is the start of clearing the air which has become really poisonous in our islands. We hope this process redeems the individual and the nature of politics in one go.

"We've been given £40,000 by 3,000 people in three days. It's very clear that people are fed up with people lying to keep office and they want something done about it.

"We would like Alistair Carmichael to stand down, that's clear from this process, but we want him to stand down so that if he wants it, if the courts consider him fit, he can have the second chance. But it's up to us, the people, to give it to him."

Morrison said he was a member of the SNP but denied that the campaign was politically motivated. He pointed out that the money had come from individuals and "not from any political party or from any campaign group".

He said: "I am here as a voter in the constituency, if you look at the website you will see people from every political persuasion in Scotland have been contributing money."

Morrison said he was "humbled" by the level of donations to the campaign, but added: "The reality is we will need more, maybe a lot more because litigation costs and we are personally liable for all of this."

Holland said no further details of the legal action, lodged under the Representation of the People Act 1983, would be revealed until the petition had been formally served.

Carmichael became Scotland’s only LibDem MP after 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 if he was still a government minister and has declined his ministerial severance payment.

The MP was backed by local Liberal Democrats earlier this week and party officials have said he will not face any internal disciplinary proceedings.

The Parliamentary Standards Commissioner Kathryn Hudson is considering complaints about his conduct and Police Scotland has also received a complaint.

A Police Scotland spokesman said: "Inquiries are continuing in consultation with the Crown Office, to whom we will report our findings."

SNP MP Pete Wishart said: "We have been clear that Mr Carmichael must consider his position - but what today's events show clearly is the strength and depth of feeling among many ordinary people in Orkney and Shetland about his conduct."

In an interview with his local paper The Orcadian, Carmichael said he’s been through “the worst five days of my life”, adding that his part in leaking the memo was a “serious error of judgement”.

He said: “For that, I have apologised to the First Minister, to the French ambassador, and I also apologised to the locale people here in Orkney and Shetland, not just for what I did, but because I wasn’t wholly truthful about it.

“I’m not going to hide from that, not going to deny it and I’m not going to obfuscate.”

In a column for the same publication, Carmichael added: “One of my biggest regrets about my current position is that I have inevitably contributed to the already low esteem in which politics is held.”

That was a view echoed on Radio Scotland’s Big Debate, when Tory MSP Liz Smith said: “Politics at the moment is not a very popular theme for many people in the population – it has lost its integrity in so many ways, and I think this is an example of a lack of integrity.”

She added: “Personally I think it would be better if he stood down.”