The June 23, 2016 Brexit referendum vote brought the United Kingdom's future into question as England and Wales voted to leave the European Union while Scotland and Northern Ireland voted to stay.
Scotland's first minister Nicola Sturgeon wrote to British prime minister Theresa May on Friday formally demanding that Ms May allow a second referendum on Scottish independence ahead of the UK's exit from the EU.
Scottish Liberal Democrat leader Willie Rennie said: "There will be many voters who voted to remain in the European Union who will be feeling betrayed by the SNP who are simply using Brexit for their own ends".
May has insisted "now is not the time" for another referendum, but she now faces a battle on two fronts as she seeks to negotiate a good deal from Brexit and tame nationalist sentiment in Scotland.
UK Prime Minister Theresa May says the start of the Brexit process means it's not the right time for another vote on Scottish independence.
Scots rejected independence in a 2014 vote by 55 to 45 percent, but Sturgeon says circumstances have changed because, while the United Kingdom as a whole voted for Brexit, Scots strongly backed remaining in the EU.
The Scots want the vote to take place between autumn 2018 and spring 2019.
He said that Westminster will respond in due course but ruled out discussions on second independence referendum.
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Sturgeon's predecessor Alex Salmond frequently threatened to hold a non-binding "consultative referendum" in 2012, before London relented and approved the legally binding poll in 2014.
It followed a Scottish Parliament vote last week in which MSPs backed the SNP administration's bid to pursue another ballot.
"It is my firm view that the mandate of the Scottish parliament must be respected and progressed", Sturgeon wrote in her letter to the Prime Minister, according to the Press Association.
A hard copy of the letter will be sent to Downing Street, with a PDF file emailed as an attachment.
"The Scottish government's mandate for offering this choice is beyond doubt", she said.
"I hope that will be by constructive discussion between our governments", Sturgeon continued.
Ms Sturgeon has called for the referendum to take place after the final terms of the Brexit divorce are agreed.
In a video message posted by the Scottish Government on Twitter, she said: "The next two years are hugely important for Scotland because they will determine the kind of country we'll become".