Image copyright PA Image caption Ruth Davidson said the SNP could negotiate for a new referendum agreement if they won an outright majority at Holyrood

The UK government should only agree to a new Scottish independence referendum if the SNP wins a majority in the next election, Ruth Davidson has claimed.

First Minister Nicola Sturgeon insists she has a mandate for a new vote on independence, and says it would be wrong for UK ministers to block one.

But the Scottish Conservative leader said only an "outright majority" for the SNP at Holyrood would be a mandate.

All 10 Tory leadership candidates have voiced opposition to a new referendum.

Ms Sturgeon has called this position "unsustainable", and wants a new vote to be held in the second half of 2020.

The SNP leader wants a deal with the UK government, similar to that agreed for the 2014 referendum, before she calls a fresh vote.

Ms Davidson agreed that this approach was the "gold standard", but argued that Ms Sturgeon does not currently have a mandate to negotiate such an agreement.

The SNP's manifesto for the 2016 Holyrood election stipulated that a new referendum could be held if there was either "clear and sustained evidence" that a majority of Scots wanted independence, or a "significant and material change in circumstances", like Scotland being taken out of the EU against its will.

In light of this, Ms Sturgeon stepped up planning for a vote after the EU referendum, which saw 62% of Scottish voters back Remain while the UK as a whole voted to Leave.

However, Ms Davidson argued that the SNP had lost its majority in the 2016 election, and also had lost votes and seats in the 2017 general election.

Image copyright Getty Images Image caption The SNP's 2016 manifesto called for a new referendum in the event of a "significant and material" change in circumstances

She told BBC Scotland: "The last time the SNP went to form the Scottish government, they had their majority taken away from them. They then asked for a second referendum, and lost half a million votes at a snap general election and lost 21 seats across the country.

"They're currently polling about 37%, that's what they got at the European election. Don't get me wrong, that's a good result for any party, but it's not a majority. And Nicola Sturgeon herself has said she only has the right to hold another referendum if a majority of Scots want it."

Pressed on what would give Ms Sturgeon a mandate for a new vote - dubbed indyref2 - Ms Davidson said that only "another majority in a Holyrood election" would be enough.

She said: "If she puts it in a manifesto that she's going to hold another referendum and she wins a majority outright, then she can negotiate with the UK government in the same way as happened last time.

"But she doesn't get to just, in the middle of a parliament where she's lost her majority, get to stick her hand up and say I'm going to re-run this referendum again and again until I get the result I want."

Image copyright Getty Images Image caption The UK and Scottish governments - led by David Cameron and Alex Salmond - signed an agreement for the 2014 referendum

Ms Sturgeon has put forward framework legislation which could pave the way to indyref2 at Holyrood, but has held off from formally requesting a transfer of powers from Westminster to hold it.

She has indicated that she is waiting for the Conservative leadership contest to run its course, as well as more clarity about the outcome of Brexit.

Speaking during a visit to Brussels on Tuesday, Ms Sturgeon said: "We don't even know who the prime minister is going to be. There is no UK government worthy of the name right now.

"So I've made the decision that in the Scottish government and the Scottish parliament we will do the bits of the process that we are able to do, get on with that, and we'll come to the issue of the transfer of power at an appropriate point.

"But the question really should be put to the UK government. It's one thing to oppose independence, it's a completely different thing to stand in the way of Scotland having the right to choose. That is not, in my view, a position that is sustainable."

Asked if she would have to win another election in order to break the current impasse , Ms Sturgeon told BBC Scotland: "I don't accept that".

She added: "I have a mandate won at the 2016 election to offer the people of Scotland a choice in the very circumstances we're in now.

"I don't think anyone should accept that a UK government has the right to ignore and undermine and negate a democratic mandate of the Scottish government. I think any democrat should challenge that position."