Former SNP leader Alex Salmond has said he would expect another referendum on Scottish independence within two years of a Brexit vote, in a BBC EU debate.
He said if Scotland is "dragged out" of the EU "against our will" on 23 June, he believed there would be another vote - and it would back independence.
But Conservative Liam Fox said the EU vote should not be "stoked by fear" of a second Scottish referendum.
Voters aged 18-to-29 took part in the BBC debate in Glasgow.
Ahead of the EU referendum on 23 June, the at-times feisty debate - entitled How Should I Vote? - also included Labour's Alan Johnson, who backs staying in the EU, and UKIP's Diane James, who is campaigning for a Leave vote.
Former First Minister Mr Salmond, who backs remaining in the EU, told the audience a second Scottish independence referendum "would have to be within the two-year period of the UK negotiating to withdraw" from the EU, should it vote to leave.
He said: "If you had the situation where Scotland, in four weeks' time, votes Remain and the rest of the UK or England drags Scotland out by voting to leave, then that would justify, in my opinion, another referendum."
"In the circumstances of Scotland being threatened with being dragged out of the EU against our will, I think the result would be 'Yes' this time."
But Leave supporter Mr Fox accused Mr Salmond of "yet another fear campaign about a Scottish referendum".
Mr Fox said: "I have never been very sure what the SNP didn't understand about the result - the Scottish people voted to stay in the UK."
He said the EU referendum was "a decision that we take as the UK... every vote counts.
"It's a decision for all the people in the UK and we should take it on the merits of the European Union debate and not be sidetracked into yet another fear campaign about a Scottish referendum."
BBC political correspondent Iain Watson
It was lively. It was feisty. And that was just the audience.
The BBC referendum debate gathered together 18 to 29-year-olds from all over the UK to hear four panellists, the youngest of whom - 54-year-old Liam Fox - was a quarter of a century older than the oldest member of the audience.
But the most striking contribution came from 60-something Alex Salmond.
The former first minister of Scotland didn't just want to talk about this referendum, but the next one.
Read more from Iain.
During a wide-ranging discussion, the audience criticised both campaigns for using the economy and immigration to "get the emotions ramped up".
Mr Salmond said he did not buy into some of the "scaremongering" material put out by the Treasury on the Remain side, adding: "It wouldn't be economic apocalypse if we left the EU but there's more jobs and more chances if we stay in."
He said: "That's not the way to conduct referendum campaigns... The remain campaign can't afford to lose 1% a month, otherwise they will lose.
"To win a campaign to motivate people you have got to argue a positive case."
Some of the young voters taking part criticised "tit-for-tat" attacks during the campaign, describing it as "petty name-calling" and saying it was no wonder people did not know which way to vote.
UKIP's Ms James did not accept that some in the Leave side's focus on immigration had been "appalling".
She said there had been a focus on migration "on the basis that that's one very clear example that the UK government.. actually don't have control over a key aspect of our economy".
Other issues raised during the debate included travel, the NHS, house prices and jobs.
Asked whether travel across Europe would be affected by a vote to leave, Mr Fox said: "Europe and exchange and trade and travel existed before there was a European Union and will continue after.
"Why do we have these arrangements? Because it is genuinely in the interests of both parties to do so."
But Labour's Mr Johnson said: "At the moment, we have a very beneficial system we can go anywhere within the EU, it's a two-way process...
"There are 2.5m tourists who come to Scotland every year. How are you going to differentiate between the Polish plumber and the Polish tourist? It means surely, a system of visas."
He added: "Unless you put a border and watchtowers across the borders between the Republic of Ireland and Northern Ireland, you're going to have people coming across there because you're going to have an EU country and a non-EU country."
Asked whether visas would be required for European travel in the event of a Brexit vote, UKIP's Ms James said: "We just don't know".
She said the PM should have identified that sort of detail already but had not published a "Plan B".