A VETERAN SNP politician has hit out at calls to hold an “advisory” referendum on Scottish independence without the UK Government’s approval.

Pete Wishart, chair of Westminster’s Scottish Affairs Select Committee, said this could “significantly” set back the independence cause.

Party figures including Joanna Cherry, the SNP’s home affairs spokeswoman at Westminster, have suggested such a move could provide a way forward.

Ms Cherry suggested Holyrood should pass a Bill to hold a consultative referendum, and then let Boris Johnson mount a legal challenge on whether it has the power to do so.

She said: “The balance of legal opinion is that we might well win any court challenge, and I don’t believe that losing would set us back any further than where we are just now.”

But Mr Wishart – the SNP’s longest-serving MP – said pushing ahead with an advisory referendum would be “anything but consequence free”.

Writing on his website, he said: “It is something that could set us back significantly and could also unleash a range of forces that could quickly escalate out of control.”

He said the UK Government would “boycott the whole process and refuse to engage and acknowledge any result”.

Even if an advisory referendum was declared legal, Mr Wishart argued the Yes side would need to win over half the electorate “as the boycotters would claim ‘victory’ with anything less”.

He said: “This is a huge threshold to achieve and would have to be done with co-operation from unionist local authorities who may not be particularly well disposed to participate in such a referendum.”

The Perth and North Perthshire MP said the UK Government could also “decide to change the law as they did with the Scottish Government’s [Brexit] Continuity Bill and retrospectively declare any poll illegal”.

He added: “With the UK refusing to accept the result we’d be right back to roughly where we are having indulged in a one sided supra-opinion poll that may or may not have given us a useful result.

“More worryingly there could be pressure to use the result as a mandate for independence and simply declare UDI [unilateral declaration of independence] with all the Catalan-style consequences and impacts on our international standing.

“In the meantime the people of Scotland will be observing all of this and we can only start to imagine what their reaction might be.”

Mr Wishart urged independence supporters to “keep our patience and constraint and not set out along a route that could be playing into our opponents’ hands and could set us back years”.

He argued things will come to a head at next year’s Holyrood elections.

If there is a clear majority for independence, the UK Government will have “no available grounds” on which to resist another referendum, he said.

SNP MP Angus B MacNeil, who represents the Western Isles, said he respectfully disagreed.

Writing on Twitter, he said: “Currently Boris has Pete & his thinking in a corner. Unlike the present of the December election given to Boris, Boris does not give presents in return.

“It is easy to keep a one trick approach in a corner! Thatcher did for 18yrs.”