PRESSURE continued to mount on shamed former Scottish Secretary Alistair Carmichael to resign as an MP last night after a newspaper column from 2010 came to light in which he stressed the need for members of Parliament to “tell the truth”.

The SNP said the Liberal Democrats’ sole remaining MP in Scotland should abide by his own code and stand down as MP for Orkney and Shetland. He had also supported an Early Day Motion on the right of recall for MPs who are found guilty of serious wrongdoing to stand down and face a by-election.

The developments came as a former leader of the SNP questioned the delay in publication of Sir Jeremy Heywood’s inquiry in the false memo Carmichael leaked about Nicola Sturgeon’s conversation with the French ambassador. Gordon Wilson suggested there had been an Establishment cover-up during a sensitive election period.

Carmichael is also facing an inquiry by Kathryn Hudson, the Parliamentary Commissioner for Standards.

Mike MacKenzie, SNP MSP for the Highlands and Islands, said: “Just when Mr Carmichael thought things couldn’t get any worse he has been caught in breach of his own code – and this further deepens the credibility crisis he now finds himself in.

“Mr Carmichael’s newspaper column in the Shetland Times, where he cites the dangers of political smears and the need for MPs to be truthful, along with his support for the right of constituents to recall their MP, leaves his position increasingly perilous.

“Mr Carmichael misled his constituents during an election, and the only way that he can relieve the pressure he is under is to stand down.

“There are also questions for Scottish LibDem leader Willie Rennie and indeed former LibDem UK leader Nick Clegg to answer – what did they know, and when did they know it? We need to know the answers to these questions, especially now that we know the LibDems aren’t prepared to take any action at all.”

MacKenzie added: “Had Alistair Carmichael admitted the truth before polling day, he would have been a discredited candidate and the result may well have been different – it’s possible he would have gone the same way as every other LibDem MP in Scotland and been turfed out by the voters.

“Mr Carmichael’s majority plummeted from nearly 10,000 to just over 800, and there appears to be a very strong reaction in Orkney and Shetland against him this weekend. The people in his constituency deserve to know the whole truth, and in my view would be best served by Mr Carmichael standing down.”

Danus Skene, who was the SNP’s General Election candidate for the Northern Isles, said the people of Orkney and Shetland had been left with an MP of questionable integrity.

“Mr Carmichael has now admitted responsibility for the authorisation of the leak,” he said.

“This amounts to an admission that he lied. He could and should have come clean at the time. This would have been before the election, and before the expenditure of time and money pursuing an inquiry to establish the truth.

“As it is, the people of Orkney and Shetland were kept in the dark by a cover-up, and find themselves to have elected an MP of questionable integrity whose standing in the Commons is fatally undermined. We in the isles cannot consider ourselves to be effectively or honourably represented.”

Skene added: “The SNP in the isles stands ready to contest any new election to select an appropriately focused MP of integrity.”

Wilson, who led the SNP through the 1980s, questioned why Heywood had delayed the report of his investigation until after the election.

He told The National: “In all the demands for Carmichael to reconsider his position, there seems to have been little examination of the timing of the report.

“The Cabinet Secretary promised an investigation of the leak. This leak was an attempt through the Liberal Democrat Secretary of State for Scotland, a representative of the coalition government, to smear Nicola Sturgeon.

“It had a bearing on the General Election and was used by the Conservative wing of the coalition to attack the Labour Party. It was a live issue.”

He added: “The Civil Service is supposed to be neutral. In this case, its neutrality was very one-sided.

Was it an Establishment cover-up during a sensitive election period? If not, why the delay?”

Protests were held in Orkney and Shetland over the weekend, calling for Carmichael to quit, and an online petition calling for his resignation had attracted more than 10,300 signatures last night.