A Panelbase survey for The Sunday Times and Heart radio station found that 17 per cent of adults - or about 700,000 people - would think about leaving after independence.
In contrast, 5 per cent - about 200,000 voters - said they would consider emigrating after a No vote, with 73 per cent saying they plan to stay regardless of the outcome.
The poll of 1,041 people puts support for independence at 41 per cent, up one per cent since the last Panelbase poll for The Sunday Times and Heart in May.
The No vote was also up one per cent to 48 per cent while 11 per cent are yet to make up their minds.
When undecided voters are excluded, the Yes vote stands at 46 per cent and No support is at 54 per cent.
The poll found that 34 per cent of people think Scotland will be better-off under independence while 42 per cent believe the country will be worse-off.
The results have been welcomed by both sides in the referendum campaign.
Yes Scotland chief executive Blair Jenkins said: “Support for Yes is solid and as we move into the final eight weeks of the campaign we will be working hard to continue the flow of undecided voters to our side.
“What this poll confirms is that, in spite of a renewed barrage of scaremongering and relentless negativity from the No camp and Westminster government, we are in touching distance of success on September 18. We need just over a four-point swing to put us in front.
“The greater strength of our huge grassroots campaign is of crucial importance. In a million conversations around the country, people are seeing a Yes vote as a unique opportunity to create a better Scotland.
“With independence we can make decisions that match our own needs, priorities and aspirations.”
Better Together campaign director Blair McDougall said: “This poll is a blow to Alex Salmond’s faltering campaign and makes clear that the momentum is with those of us saying no thanks to separation.
“The closer we get to the referendum the more people are thinking seriously about the consequences of independence for the pound, pensions and our public services.
“The majority of Scots looking at Alex Salmond’s failure to provide honest and credible answers are simply saying no thanks to taking on so many risks.
“We can have the best of both worlds for Scotland - a strong Scottish Parliament, with more powers for Scotland guaranteed, backed up by the strength, security and stability of being part of the larger UK. Only separation puts that at risk.”