The Scottish First Minister Nicola Sturgeon has criticised a decision by British Prime Minister Boris Johnson to refuse a second independence referendum in Scotland.
In a letter to Ms Sturgeon, Mr Johnson said: "You and your predecessor made a personal promise that the 2014 independence referendum was a 'once in a generation' vote.
"The UK government will continue to uphold the democratic decision of the Scottish people and the promise you made to them.
"For that reason, I cannot agree to any request for a transfer of power that would lead to further independence referendums."
Scottish people voted by 55% to 45% to stay in the United Kingdom in a referendum in 2014.
But calls for a new poll have grown since the Brexit referendum, where Scotland voted in favour of staying in the European Union.
The Scottish National Party (SNP) also says that its success at the last UK general election, where it won 48 of Scotland's 59 seats in Westminster, suggests there is a desire for a new vote.
A march for Scottish independence in Glasgow on Saturday reportedly attracted tens of thousands of people.
— Nicola Sturgeon (@NicolaSturgeon) January 14, 2020
Ms Sturgeon called Mr Johnson's response "predictable - but also unsustainable and self defeating.
"Scotland will have the right to choose".
She said: "The Tories are terrified of Scotland having the right to choose our own future.
"They know that when given the choice the overwhelming likelihood is that people will choose the positive option of independence."
"The longer they try to block a referendum, the more they demonstrate that the Westminster union is not a partnership of equals and the more support for independence will grow".
She added: "The Scottish Government will set out our response and next steps before the end of this month - when we will also again ask the Scottish Parliament to back Scotland's right to choose our own future."
Ms Sturgeon had previously said she wanted to hold a second independence referendum by May 2021.
At the time, she retweeted an advert from her party's 'Yes Scot' campaign.
It showed a man waking up in Scotland and hearing about how much Brexit is costing.
A knock on his front door revealed Ms Sturgeon, who simply says: "You know we can do so much better than this.
"Go and get your jacket - it's time".
Westminster isn’t working for Scotland. We’ve been ignored too often. It’s time for a fresh start – to choose a different and better path.
— Yes (@YesScot) April 24, 2019
A campaign guide, focused on Scotland's economic potential as an independent country, was also to be distributed to every home.