An SNP MP has claimed “there could be mileage” in a consultative referendum on independence if Boris Johnson does not grant an official one, according to reports.

Mhairi Black made the comments in the Sunday Times as the First Minister gets set to lay out the next steps towards a fresh ballot.

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The SNP leadership has consistently stressed it does not support an unofficial independence vote and Ms Black has become the most senior figure to give some authority to the idea.

An unofficial referendum would be open to a legal challenge. 

She told the newspaper: “There could be mileage in a consultative referendum because the Scottish question is complicated.

“The current United Kingdom government position is weak and unsustainable, and if the last five years proves anything, it proves that what happens at Westminster is unpredictable.”

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The MP for Paisley and Renfrewshire South added her preference would be to do the next referendum “by the book” and that an official referendum would ensure international recognition.

She accepted a vote "would then no doubt be challenged in the UK Supreme Court and the Supreme Court would have to make a decision."

Black also said that she would support a referendum on whether Scotland should retain the monarch saying: Personally I'm not a monarchist, I've always been a republican and I would like to think there is a majority of Scots who take that view. Why is there a single family we all have to fork out for?"

It comes after a report found Brexit will negatively impact the most vulnerable people in Scotland, with the paper, commissioned by the Scottish Government, identifying 137 potential impacts on those already facing inequality, discrimination, or social exclusion.

Pamela Nash, chief executive of Scotland in Union, said: “These senior Nationalists just don’t get it. The majority of people in Scotland don’t want a divisive second independence referendum, and they don’t want to leave the UK.

“Just imagine if they put this amount of effort into addressing the crisis in our schools and hospitals, rather than on how to divide communities.

“Trying to get independence through the back door through a wildcat contest is simply not acceptable and would end up in an expensive legal battle.

“Nicola Sturgeon must rule out a Catalan-style referendum and get on with the job she is elected to do. Scotland deserves better.”