The latest poll by YouGov shows that the 'No' campaign is now just six points ahead of the 'Yes' campaign, down from 14 points in mid-August and 22 points early last month.
Rising by eight points in just one month, the 'Yes' campaign has narrowed down the pro-union lead. Excluding the still undecided voters, 53 per cent of those surveyed favour union, while 47 per cent support independence for Scotland.
The referendum is scheduled for September 18.
Peter Kellner, the president of YouGov, said while he still expected the campaign against independence to win, a victory for the 'Yes' camp can no longer be ruled out.
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"A close finish looks likely, and a 'Yes' victory is now a real possibility. If 'No' finally wins the day, it now looks less likely that it will win by a big enough margin to deliver a knock-out blow to supporters of independence," he said.
Campaigning on opposite sides, Scottish First Minister Alex Salmond and shadow Scottish secretary Margaret Curran focused on the jobs in food and drinks industry today, that also marked the last day for people to register to vote.
On a visit to Eden Mill distillery and brewery in Guardbridge, Fife, Salmond set out his vision of the gains of independence for the food and drink industry in Scotland.
"The huge publicity generated by a 'Yes' vote - and the transition to independence - will be the opportunity of a lifetime for our food and drink sector to extend its global reach even further," said the first minister.
Curran, who was visiting Glasgow's Tennent Caledonian Breweries, argued, "Around one million jobs in Scotland rely on companies based elsewhere in the UK and many more are with companies that rely on trade with England.
"Scotland cannot afford to have opportunities cut off. We want a strong Scotland backed up by a strong UK," he said.