The British government should only agree to a new Scottish independence referendum if the SNP wins the majority in the next election, Ruth Davidson has said.
First Minister Nicola Sturgeon insists she has a mandate for a new vote on independence and says it would be wrong for British ministers to block one.
However, the leader of the Scottish Conservatives said that only an "absolute majority" was a mandate for the SNP in Holyrood.
All 10 Tory leadership candidates have spoken out against a new referendum.
Ms Sturgeon has described this position as "unsustainable" and wants a new vote in the second half of 2020.
The SNP Chairwoman wants a deal with the UK government, similar to that agreed for the 2014 referendum, before requesting a new vote.
Ms Davidson agreed that this approach was the "gold standard" but argued that Ms Sturgeon currently has no mandate to negotiate such an agreement.
The Holyrood 2016 SNP Manifesto stated that a new referendum can be held if there is either "clear and sustained evidence" that the majority of Scots desire independence, or "significant and material changes in circumstances", such as the abolition of Scotland of the EU against its will.
Against this background, following the EU referendum, in which 62% of Scottish voters voted for Remain and the United Kingdom voted in favor of Leave, Ms Sturgeon intensified plans for a vote.
However, Ms Davidson argued that the SNP lost its majority in the 2016 elections and also lost votes and seats in the 2017 parliamentary elections.
She told BBC Scotland: "The last time the SNP formed the Scottish government, they were deprived of their majority, then called for a second referendum and lost half a million votes and 21 seats across the country in an early parliamentary election.
"They are currently asking about 37%, they got that in the European elections, do not get me wrong, that's a good result for any party, but it's not a majority, and Nicola Sturgeon herself said she only has that. " Right to hold another referendum if the majority of Scots so wishes. "
Asked what would give Mrs. Sturgeon a mandate for a new vote – called indyref2 – Ms Davidson said that only "another majority in a Holyrood election" would suffice.
She said, "If she states in a manifesto that she will hold another referendum, and she wins the majority right away, she can negotiate with the British government as she did the last time.
"But she can not simply hold up her hand in the middle of a parliament where she has lost her majority and say that I will repeat this referendum again and again until I get the desired result."
Mrs. Sturgeon has submitted framework laws that could pave the way to Indyref2 in Holyrood, but she has refused to formally request a transfer of authority from Westminster to hold it.
She has hinted that she is waiting for the conservative leadership competition to take its course, and more clarity about the outcome of Brexit.
During a visit to Brussels on Tuesday, Ms Sturgeon said: "We do not even know who the Prime Minister will be, there is currently no British government worthy of the name.
"So I made the decision that we in the Scottish Government and the Scottish Parliament are doing the parts of the process that we can, going on and coming to the issue of the transfer of power at a convenient point.
"But the question should really be addressed to the British Government, it's one thing to oppose independence, it's a very different matter to stand in the way of Scotland, to have the right to vote. that exists. " sustainable. "
When asked if she needed to win another election to overcome the current impasse, Ms. Sturgeon told BBC Scotland, "I do not accept that."
She added: "I have won a mandate in the 2016 elections to give people in Scotland a choice, just under the circumstances we are in right now.
"I do not think anyone should accept that a British government has the right to ignore, undermine and negate a Scottish government's democratic mandate, and I think every Democrat should question that position."