ANGUS Robertson, the SNP's Westminster leader, has said Scotland will become independent if Nicola Sturgeon calls a second referendum in the wake of last month's Brexit vote.

The Moray MP said the vote to leave the EU had already shifted public opinion in favour of Scotland breaking away from the UK.

In an interview with The House magazine, he also warned the next Prime Minister not to block a second referendum.

Ms Sturgeon has embarked on a diplomatic charm offensive to explore possible ways of keeping Scotland in the EU after Scots voted to remain by 62 per cent to 38 per cent.

However, she has admitted an independence referendum is "highly likely" as the means for Scotland to become an EU member state in its own right.

She has said it would be held within the two year negotiating window before Britain formally leaves the EU.

Labour is examining a possible federal set-up for the UK that would allow Scotland to remain in the EU but the plan is in its infancy.

Predicting victory for a future Yes campaign, Mr Robertson - who is standing for his party's deputy leadership - said: "It (Brexit) has already changed public opinion in Scotland. Every single opinion poll since the Brexit referendum has shown a majority for Scottish independence.

"People who had previously not supported Yes and wished to remain in a UK that was in Europe and were promised that a No vote in 2014 was the best way to guarantee Scotland’s place in Europe are now learning to their bitter cost that that was not true.

"We’re seeing a range of people from different political parties and none who say that things have changed completely.

"The UK that people were voting to stay part of in 2014 does not exist in the same way as it did."

He added: "I hope Scotland is independent as soon as is practically possible. We’ve got a big job to do and England and Wales have effectively declared independence from the United Kingdom, and the challenges that we face in protecting our economy and our place in the European market is profoundly important,

"These things matter and the clock is ticking, which is why the Scottish government and the SNP is seized of the challenge which has been placed on us."

In a message to the Tory leadership candidates, he said the next PM should not withhold legal backing from another referendum.

David Cameron has previously said the Scottish government should stick to its promise that the last referendum - which the pro-Union side won 55% to 45% - would be a "once in a generation" event.

However, Scottish Tory leader Ruth Davidson last week said Westminster must not withhold its permission for Holyrood to have another one if it wants to.

Kezia Dugdale, the Scottish Labour leader, has also said Westminster should not block a referendum if Scots wanted a second vote.

Mr Robertson said: "There’s practically nobody serious in Scottish politics who believes that if there is a demand for a second Scottish referendum that it won’t happen.

"We live in a democracy in both Scotland and the UK and I think any incoming Tory PM who stood in the way of Scottish democracy has no idea what damage they would be doing."