YES supporters should vote to remain in the European Union on Thursday if they want a second independence referendum in the foreseeable future, Nicola Sturgeon says today.

After a series of new polls showing Leave and Remain neck and neck, the First Minister says one of her key arguments for a new referendum would collapse if there was a Brexit vote on both sides of the border.

Only a mismatch between Scotland and the rest of the UK over Brexit would give her a mandate for an independence ballot, she writes in the Sunday Herald.

She tells voters: “If you are basing your decision on what it means for independence, let me be very clear – the only sensible and logical vote is one for Scotland to remain in Europe."

Some polls including a YouGov poll for ITV today puts Leave on 44 per cent, Remain on 42, and undecideds at nine.

The online survey of 1,734 adults was conducted between June 15 and 16, meaning some people were questioned before the murder of Labour MP Jo Cox.

Others have the sides pegged at 44% each.

Sturgeon’s message is a rebuke to senior Nationalists backing Leave, such as former SNP deputy Jim Sillars, who argue Brexit would remove the EU as a roadblock to independence.

Instead, she argues that not only is Remain best for Scotland and the UK because of access to the single market and workers’ rights, it is also best for the Yes movement.

The SNP manifesto in May said Holyrood should have the right to hold another referendum “if there is a significant and material change in the circumstances that prevailed in 2014, such as Scotland being taken out of the EU against our will”.

Sturgeon says she hopes the scenario does not arise, but if it does “then the option we set out in our manifesto must be on the table for consideration. But that option only arises if Scotland votes Remain. If Scotland votes to leave, then that reason for independence doesn’t arise.”

If the result is for Brexit, the First Minister plans to “seize the narrative” amid Labour and Tory disarray on Friday by asserting Holyrood's right to hold a second referendum.

Under one scenario considered by the SNP government, Scotland would stay in the EU, either as a full or shadow member during negotiations, as the rest of the UK pursued Brexit.

“Europe can be very creative on such things,” said a government source.

Tom Harris, the Director of Vote Leave Scotland, accused Sturgeon of panicking.

He said: “She’s clearly worried that, having come out so strongly for Remain, her own authority will be undermined if SNP supporters ignore her advice. But Thursday is not about her or independence, it’s only about the UK’s future with Europe.”

Despite reports of plotting by Tory MPs to oust him, Cameron yesterday insisted he would continue in Downing Street if the country rejected his pleas for a Remain vote.

Asked if he would stay, he told the Times: “Yes. It won’t be a verdict on me, whatever the outcome is. It’s a verdict on the question, but I do care a lot about the question.”

Vladimir Putin suggested the Prime Minister had called the referendum to "scare" Europe.

In his first intervention on the subject, he said: “Why did he initiate this vote in the first place? Why did he do that? So he wanted to blackmail Europe or to scare someone, what was the goal if he was against?"

Foreign secretary Philip Hammond claims Putin wants Brexit as it would weaken Europe.

However, the Russian president declined to state his preference or make a prediction.

"I have my own opinion on this matter. I cannot talk about the result yet. I think it is 50-50 with a certain margin of error," he said.

Meanwhile the UK’s former defence chief Lord Guthrie announced he had switched sides to the Leave campaign as he was worried by the prospect of "a European army".

The BBC also announced last night that Ruth Davidson would square off against Boris Johnson in its final TV debate of the campaign on Tuesday.

The Scottish Tory leader will argue for Remain alongside London Mayor Sadiq Khan and TUC general secretary Frances O'Grady at the SSE Arena Wembley.

Johnson will again team up with Tory energy minister Andrea Leadsom and Labour MP Gisela Stuart, the same line-up who appeared in the recent ITV debate.

SNP Transport minister Humza Yousaf will also feature in the event.

Scottish LibDem leader Willie Rennie will today invoke the memory of the late Charles Kennedy in a speech to activists in Paisley, saying the former party leader’s idealism about Europe is sorely missed after “a dark week for freedoms and democracy”.

Meanwhile, a new survey has identified European cooperation against terrorism as the most important factor influencing the vote of young Scots, closely followed by human rights.

The online poll of 619 people aged 11 to 25 run by Young Scot found 87 per cent cited security issues as important in how they would vote on Thursday - or how they would vote if old enough - with 63 per cent ranking it as “very important”.

Equal rights was important to 85 per cent, with 64 saying it was very important.

Education, the environment, the single market and immigration were also key factors.