Glasgow (AFP) - Support for Scottish independence is increasing three weeks ahead of a referendum, a poll published Friday showed, amid attempts by British Prime Minister David Cameron to make the business case for retaining the union.
Cameron on Thursday urged Scottish people to reject independence in a rare speech in Glasgow in which he argued the union was a strong economic advantage.
However the ranks of those who want to end more than 300 years of union with the rest of the United Kingdom appear to be swelling.
A Survation survey found 47 percent of respondents would vote "Yes" to independence, compared to 53 percent who would vote "No", excluding people who were undecided.
This was a considerable narrowing of the gap between the two sides in a similar poll three weeks earlier, in which 43 percent said they would vote "Yes", versus 57 percent who would vote to remain in the union.
The poll was commissioned by the Scottish Daily Mail newspaper to assess reaction to the final public debate between the leaders of the pro and anti-independence campaigns.
"Yes" campaign leader and Scottish First Minister Alex Salmond was widely seen to have won the debate against "No" campaign leader Alistair Darling.
Cameron said the union between Scotland and England was the "greatest merger in history" as he addressed a conference of the Confederation of British Industry (CBI) in Glasgow.
His visit came on the day that 200 company heads signed an open letter to say independence was in Scotland's "best interest" -- underlining the polarised views over the issue three weeks from the September 18 referendum.
Questions over whether Scotland's economy could do well alone have been at the heart of the campaign.
The "Yes" and "No" camps have traded statistics and accusations on everything from whether Scotland could keep using the pound to what share of Britain's national debt it should take on if it broke away.
Cameron had kept a low profile on the campaign trail, due to his centre-right Conservative Party's unpopularity in Scotland.
But he re-entered the fray in his speech on Thursday, saying the UK was "one of the oldest and most successful single markets in the world" and that Scotland does twice as much trade with the rest of the UK as the rest of the world put together.
"Our single market is one of our union's greatest advantages. If we stay together, Scottish businesses have better opportunities, Scottish consumers have more choice and Scottish people have more secure jobs," Cameron said.
"Why put that great advantage at risk by going into the great unknown?"
- 'Cameron isn't welcome' -
Outside the venue for Cameron's speech, about 120 protesters gathered, chanting and waving the Scottish blue and white flag and banners such as "Another Scotland is Possible".
"I've got friends and family who go to a food bank every day to get food to feed their kids because the living wage they've got is not enough," said Michael Larkin, 34, an illustrator.
Other protesters criticised the austerity policies of the Conservative party, which has just one MP out of 59 in Scotland, where the opposition Labour party is far more popular.
"David Cameron isn't welcome in Scotland because Scotland don't vote Tory (Conservative)," said Samuel Cook, 18, a student.
"I want independence because I want Scotland to make its own decisions. I want to get rid of the Tory party because Scotland has a Tory government we do not vote for," he said.
The pro-independence campaign argues that the British government's economic policies are unfairly skewed in favour of London and southeast England.
Salmond greeted the pro-independence letter from business leaders by declaring industry was "waking up to the opportunities of independence".
The signatories range from big business leaders such as Brian Souter -- chairman of major transport group Stagecoach and a prominent donor to the independence campaign -- to the owners of smaller enterprises such as guest houses.
Think tank Capital Economics added to the debate on Thursday, warning that independence could lead to significant capital flight from Scotland's giant finance industry.