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Ex-European Council president Herman Van Rompuy suggested Brussels would find it harder to stomach a vote for Scotland to breakaway from the rest of the UK if it hadn’t been authorised by Westminster. Ms Sturgeon has consistently threatened a fresh independence referendum since last summer’s Brexit vote, with the First Minister insisting Theresa May must listen to her demand for a “differentiated” exit deal for Scotland. The SNP leader has also described Scotland staying in the EU as an independent member state as the “best option” for the country. But former top EU boss Mr Van Rompuy advised Ms Sturgeon the way the SNP pushes for a second referendum would affect Brussels’ view of a possible successful vote for Scottish independence.

GETTY Herman Van Rompuy warned Nicola Sturgeon over a 'unilateral' move for a referendum

Asked how the EU should deal with Scottish independence if nationalists won a referendum, Mr Van Rompuy told an audience at Chatham House this morning he would “never answer hypothetical questions”. But the former Belgian prime minister also said: “There is a difference between a unilateral move of Scotland and - whatever the outcome may be - a referendum with the consent of Westminster.”

There is a difference between a unilateral move of Scotland and a referendum with the consent of Westminster. Herman Van Rompuy

The 2014 Scottish independence referendum was agreed after Westminster granted temporary powers to the Scottish Parliament to hold a vote. It is likely a similar arrangement would have to be reached between Edinburgh and London for a second referendum to be held - although Ms Sturgeon could call for the Scottish Parliament to authorise a non-binding referendum without consulting the UK Government. The SNP are two votes short of a majority in the Holyrood parliament, although the Greens have promised to back a bid for a second independence referendum should Ms Sturgeon’s party propose a bill.

Sturgeon's top moments Fri, December 9, 2016 Scotland's First Minister Nicola Sturgeon in pictures. Play slideshow Getty Images 1 of 33 Nicola Sturgeon visits Glaxo Smith Kline.