SNP 'captured and controlled by UK spies' - the bizarre claims from party's MSP

He alleged that spies, who he refers to as security service “assets”, have been able to rise through the party into positions of considerable influence.

“It was, and remains, insane to think that the British State would not have infiltrated the SNP,” he wrote.

Martin believes that the SNP’s focus on gender policies was being pushed by the British agents in an attempt to make the party unpopular.

He claimed that by focusing on gender policies, the spies are trying to make the SNP unelectable and discredit the idea of another referendum.

In his blog post on a pro-independence website, Martin wrote: “British State assets in the SNP have, over the intervening years, risen through the ranks and now hold senior positions that have allowed them to influence party policies and direction, such as adopting a lack of urgency in delivering independence…and that’s putting it mildly.”

He added: “The SNP is completely compromised, it has been captured and controlled by the British State.”

The 63-year-old became a MSP in 2003, though he was suspended a year later after he criticised John Swinney’s leadership of the party.

Martin pointed out that the secret service had spies in the IRA and National Union of Miners, in efforts to back up his opinion.

He said: 'It would be more extraordinary if they ignored the SNP, which is a party which supposedly wants to break up the British state.

“If they hadn't infiltrated that organisation there would be something far wrong.”

Claims of British spies within the party have been made by other senior SNP figures in the past, but the accusations were mocked, with critics saying the party did not need any help in “imploding”.

Andrew Neil lambasted the former MSP’s claims online.

He wrote: “Former SNP MSP blames this year's Scot Nat implosion on British spooks who have supposedly infiltrated the party right up to cabinet level?

“Not sure MI5 that good (though it is headed by a Scot and University of Glasgow graduate). Nor do I think the new First Minister and his supporters really needed any help to implode his party.”

Blair McDougall, who ran the campaign to keep Scotland in the Union, also chimed in on the bizarre claims.

He shared a photo of Humza Yousaf edited to look like a stereotypical spy and said: “As a former MSP says the SNP is now controlled by MI5 sleepers, it's a good day to ask: are Humza Yousaf's London handlers behind the failure to prepare a basic economic case for leaving the UK?”

However, Martin was not completely alone in his belief that British state assets had weaselled their way into significant positions of power with the party.

Former deputy leader Jim Sillars told the Times: “There were a couple of people in the party who I was absolutely certain were MI5 plants. There is nothing we can do about it. We are a constitutional national organisation and, therefore, we never set up a counter-intelligence department within the party.”

Ex Scottish Government minister Alex Neil agreed with Martin and Sillars, stating he is certain that in years to come, it will emerge that the British spies infilitrated the SNP.

Martin’s accusation comes just days after it emerged that the Glasgow University students who stole the Stone of Destiny from Westminster Abbey in 1950 were given up by spies within Scotland.

The Stone of Destiny was the seat where Scotland’s monarchs were crowned in ancient times.

It was seized by Edward 1, the King of England, in 1296 and taken to London – where it remained until 1950 when the four students stole it.

Alex Neil said: “I have no doubt that in decades to come, when official secrets are disclosed, it will emerge that the people who took back the Stone of Destiny were not the only ones who were betrayed by people they thought were loyal to the cause.”