Scottish government proposes that second independence referendum happen before Brexit

Sturgeon will ask the Scottish Parliament next week to approve plans for a referendum on Scottish independence that she hopes will take place in the six months leading up to the UK's likely departure date from the EU of March 2019.

Though there was a referendum on independence in 2014 the ruling Scottish National Party (SNP) said in its manifesto for elections in 2016 that it would seek a second vote if there was a 'material change in circumstances'. Sturgeon said that leaving the EU counts as such a change.

"What Scotland deserves, in the light of the material change of circumstances brought about by the Brexit vote, is the chance to decide our future in a fair, free and democratic way - and at a time when we are equipped with the facts we need," said Sturgeon today.

UK prime minister Theresa May is expected to formally notify the European Council that the UK will leave the UK in the aftermath of a Westminster vote on the law giving her that power. Both Houses of Parliament will debate and vote on the bill today and the triggering of the two year departure process could happen as early as tomorrow.

Sturgeon said that the referendum should take place between autumn 2018 and March 2019 because she wants people in Scotland to be able to choose whether to stay in the UK or leave it before the UK leaves the EU. That, she said, might offer the opportunity to retain or negotiate a different relationship with the EU.

"If the UK leaves the EU without Scotland indicating beforehand - or at least within a short time after it - that we want a different relationship, we could face a lengthy period outside not just the EU but also the single market. That could make the task of negotiating a different future much more difficult," she said.

"These considerations lead me to the conclusion that if Scotland is to have a real choice - when the terms of Brexit are known, but before it is too late to choose our own course - then that choice must be offered between the autumn of next year, 2018, and the spring of 2019," said Sturgeon.

May's spokesman told the BBC that there was no evidence that people in Scotland wanted another referendum.

"Only a little over two years ago people in Scotland voted decisively to remain part of our United Kingdom in a referendum which the Scottish government defined as a 'once in a generation' vote," he said. "Another referendum would be divisive and cause huge economic uncertainty at the worst possible time."

Westminster must give permission for the referendum to take place and it is likely that the timing, wording of the question and even the number of options on the ballot paper will be the subject of negotiations between London and Edinburgh.