Scotland's First Minister Nicolas Sturgeon said on Friday she would not rule out a test of the legitimacy of calling a consultative referendum on independence if Prime Minister Boris Johnson's conservative government continued to oppose another vote.
Speaking in Edinburgh on the day Britain left the European Union, Sturgeon said that the question of whether the Scottish Parliament had the power to approve a non-binding vote on independence had not been tested in court.
Sturgeon wants to hold another Scottish referendum, but it cannot do so without the approval of the British government.
She asked Johnson to enter into negotiations over the transfer of power for a referendum from London to Edinburgh, and she said on Friday that this step was the best way to put the legitimacy of the vote undoubtedly.
She had previously indicated that she did not wish to hold a Catalan-style referendum, which was organized without the approval or recognition of the national government.
The Spanish region declared its independence unilaterally in October 2017 after a referendum deemed illegal by the courts, causing the largest political crisis in Spain in decades.
A poll showed on Thursday that a slim majority of Scots now support independence, backed by the support of those who previously rejected a split from the United Kingdom but now backed it because of their opposition to Britain leaving the European Union.
The Scots had previously rejected a 55% to 45% separation in the 2014 referendum.