Scotland's top politician is warning that a future United Kingdom referendum on leaving the European Union could spark a new drive for independence in pro-EU Scotland.

First Minister Nicola Sturgeon on Tuesday called for a "double-majority" system in the 2017 referendum that would require the support of England, Wales, Northern Ireland and Scotland before the United Kingdom could leave the EU.

Sturgeon warned in a speech in Brussels that British Prime Minister David Cameron's "in-out" referendum to be decided by a simple majority of Britons "would provoke a strong backlash."

She says "the groundswell of anger among many ordinary people in Scotland in these circumstances could produce a clamor for another independence referendum that may well be unstoppable."

Scots voted against independence in a referendum last September.