The UK Government has been told they must "come clean" over "secret" polling which put support for Scottish independence at its highest level so far.

The SNP renewed calls for the results of the poll, which sees support for independence at 56%, to be published.

Mujtaba Rahman, a professor of political risk, wrote in the Guardian on Monday that “ministers are increasingly nervous that a Scottish breakaway is on the cards”.

READ MORE: New Independence party blocked by election watchdog

She also revealed the Cabinet was told latest polling puts support for independence at 56%.

If true, this number represents the highest level of support for independence recorded on any poll so far.

Tommy Sheppard MP has now written to Alister Jack asking where the figure comes from and urged him to release all the data the UK government holds on support for Scottish independence through "secret, taxpayer-funded polling".

He said: “With five consecutive polls putting support for independence over 50% - with the most recent putting support at 55% - it would be surprising if the Tories weren’t conducting secret polling into support for Scottish independence. It is clear that they are running scared.

READ MORE: Sturgeon: All MSPs must defend Holyrood against 'crippling' bill

“However, if they are using taxpayers’ money to carry out such polling it is incumbent upon them to publish those results.

“The SNP has repeatedly urged the UK government to release any data they hold through taxpayer-funded polling but they continue to keep any findings secret. It speaks volumes that the Tories are so desperate to hide the findings."