Nicola Sturgeon
Nicola Sturgeon says she wants the UK to 'overwhelmingly' back a 'remain' vote at the referendumYves Herman/Reuters

Pro-EU campaigners could do more harm than good if they attempt to scare the UK electorate into voting against a Brexit at the EU referendum, Nicola Sturgeon has warned.

The First Minister of Scotland outlined her positive case for keeping the UK inside the 28-nation-bloc during a Resolution Foundation event in London on 29 February.

"It is possible to generate a positive and democratic debate that leads a positive legacy regardless of the outcome of the referendum," Sturgeon told the Westminster audience.

"I hope that the debate we engage in over the next few months is a thoroughly positive one, because one of the undoubted lessons of the Scottish [Independence] experience is that a miserable and negative campaign saw the 'No' campaign lose a 20 point lead over the course of the referendum.

"I don't want to have to point out to anybody here that the 'In' campaign does not have a 20 point lead to squander. The opportunity to have a fundamental debate about the future of your country is a good opportunity if it is one that is seized."

The SNP leader also stressed that she would not like to see Scottish independence achieved through a 'leave' vote at the 23 June ballot.

But Sturgeon warned unionist Eurosceptics that a pro-Brexit decision would trigger another ballot on Scotland's future inside the UK's political system, just years after the country voted 'No' in 2014.

"It's not hard to see why that might lead to a growing clamour for a further referendum," the self-described social democrat added. "I make that point frequently because it seems to me an honest assessment of what might happen. But it's not what I want to happen.

"Yes, of course, I want Scotland to be independent. But I don't want Scotland to be independent because the UK chooses to leave the EU. I want the UK as whole to choose to say inside the EU because I think that option would be better for the rest of the UK and the EU."

A 'positive' case for the EU

The comments come after the SNP leader launched the party's pro-EU campaign, which aims to make the "positive, progressive and upbeat" case for retaining Scotland's place in Europe. Scottish government Europe minister Humza Yousaf MSP will serve as the party's campaign director.

The 'remain' and 'leave' campaigns have accused each other of scaremongering at the start of the EU referendum campaign.

David Cameron came under fire from the left when Number 10 reportedly claimed refugee camps like the "Calais Jungle" could appear in south England if the UK broke away from Brussels.

Tim Farron described the warning as "disgusting". The Liberal Democrat leader declared: "[Cameron] has shown himself to be weak, and heartless. And this campaign needs the opposite. This campaign needs strength and compassion."

The latest online opinion poll from OBR, of more than 2,000 people between 24 and 25 February, put 'leave' four points ahead of 'remain' (52% versus 48%, respectively).

A separate survey from YouGov for The Times, of more than 3,400 people between 21 and 23 February, put 'leave' on 38% and 'remain' on 37%.