The United Kingdom's top court ruled on Wednesday that the Scottish government cannot hold a second referendum on independence without approval from the British parliament, dealing a hammer blow to nationalists' hopes of holding a vote next year.

In 2014, Scots rejected ending the more than 300-year-old union with England by 55 percent to 45 percent, but independence campaigners have argued the vote two years later for Britain to leave the European Union, which the majority of Scottish voters opposed, has materially changed the circumstances.

Scottish First Minister Nicola Sturgeon, leader of the pro-independence Scottish National Party (SNP), announced earlier this year that she intended to hold an advisory independence vote on October 19, 2023, but that it had to be lawful and internationally recognised.

However, the British government in London has said it would not grant permission for another plebiscite, saying it should be a once-in-a-generation event. Polls suggest voters remain evenly split over whether or not they support independence and a vote would be too close to call.

The Scottish government's most senior law officer had asked the UK Supreme Court whether the Scottish government could pass legislation paving the way for an advisory second referendum without the approval of the UK parliament.

The unanimous verdict of five judges on the court was that it could not.

"The Scottish parliament does not have the power to legislate for a referendum on Scottish independence," said Robert Reed, the president of the UK Supreme Court.

Under the 1998 Scotland Act, which created the Scottish parliament and devolved some powers from Westminster, all matters relating to the Union of the Kingdoms of Scotland and England are reserved to the UK parliament.

The court concluded any referendum, even advisory, would be a reserved matter.

Sturgeon said the case for Scottish independence was only strengthened by the Supreme Court ruling.

She wrote on Twitter she was disappointed by the ruling, but that she would respect it.

"A law that doesn't allow Scotland to choose our own future without Westminster consent exposes as myth any notion of the UK as a voluntary partnership & makes case for Indy," she said.

"Scottish democracy will not be denied. Today’s ruling blocks one route to Scotland’s voice being heard on independence – but in a democracy our voice cannot and will not be silenced." (Reuters)