ONE in four Scots believes M15 is working with the UK Government to prevent independence, a new poll reveals.

The study, which many will see as a measure of public distrust in Westminster, found nearly as many thought next week's vote will be rigged.

The findings - from the same pollster, YouGov, that reported the lead for Yes at the weekend - were commissioned by news site Buzzfeed as it explored hostility to the British state north of the border.

It found substantial minorities suspected skulduggery by the UK Government. A total of 26 per cent said it was "probably true" that "MI5 is working with the UK Government to try and stop independence" with 55 per cent thinking this proposition was "probably false".

Another 19 per cent agreed that it was "likely the referendum will be rigged". Those polled were split evenly when it was put to them that the UK was covering up an oil find in the North Sea.

Buzzfeed's UK political editor Jim Waterson suggested the questions after hearing Jim Murphy, the Labour MP, heckled about Clair Ridge, the field west of Shetland widely tipped in the mainstream media to yield substantial resources but the subject of feverish internet rumours of a cover-up.

Mr Waterson said: "I wondered whether people believed the things I had heard on the streets. I expected 15-20 per cent to cite the Clair Ridge 'secret', not 42 per cent.

"As with the idea of the active involvement of MI5, it all seems symptomatic of a total lack of trust in anything Westminster is doing rather than an actual assessment."

Jim Sillars, the former SNP deputy leader, has long believed that UK security services have taken a watching brief over the SNP, although he too sees the poll results as indicating a lack of trust in UK institutions.

Mr Sillars said: "I have been very surprised at the number of people who have said to me 'They will fiddle the ballot', I don't believe that.

"We have always had well-conducted elections in Scotland. What people have really said is, 'We don't trust the British state'.

"Of course MI5 is involved. Their job is to preserve and protect the British State and we are saying we want to change that state.

"MI5 will have penetrated Yes Scotland, they will have penetrated the SNP and they will have penetrated the Radical Independence Campaign. That is how they operate. They did the same with the Communist Party."

A spokesman for Better Together said: "People in Scotland know that this decision is much bigger than ridiculous conspiracy theories that circulate on social media."

YouGov put the questions to 1,084 adults over three days early this month.