Support for independence has fallen to its lowest level this year with just a quarter of people in favour, according to a poll.
The proportion of people in Scotland backing independence has fallen from 33% in February to 25%, the TNS BMRB survey shows.
But support for the Union has also dropped, from 52% to 47% over the same period
More people are undecided about how to vote in next year’s independence referendum, now at 28% compared with 15% in February, according to the poll.
Tom Costley, of TNS Scotland, said: “The high number of don’t-knows could turn out to be the most significant factor in how the referendum campaign develops. Both the Yes and No camps have lost ground in 2013, which suggests that neither campaign has yet succeeded in making a strong connection with the voters in Scotland.
“The surge in the number of those who have not decided how to vote may have arisen because both campaigns have succeeded in giving rise to doubts among some who have previously backed the other side, without generating positive support for their positions. With so many undecided, there is still all to play for.”
Pollsters questioned 1,017 adults between August 21 and 27.
TNS BMRB said the new survey suggests support for independence is at its lowest since it began polling on the issue in 2007.
In August 2011 the first poll TNS BMRB carried out after the SNP’s landslide Holyrood election victory in May that year suggested 39% in support of independence.
The new survey suggests support for independence is slightly higher among younger voters, with 29% of 16 to 24-year-olds planning to vote Yes, 39% planning to vote No and almost a third undecided.
Those in this age group are the least likely to vote in next year’s referendum, with only 45% of 16 to 24-year-olds certain to vote, compared with 62% of all those surveyed, according to TNS BMRB.
Just over half of those who voted for the SNP in May 2011 will be voting Yes (55%), along with 14% of those who voted Labour, 11% of those who voted Liberal Democrat and 5% of Conservative voters.
But these survey results contrast with a Panelbase poll published on Monday which found that of those who are either certain or most likely to vote in the referendum, 44% favour independence and 43% oppose it, with 13% who do not know.
Another survey published at the weekend, carried out by YouGov, put the Yes vote at 29% and the No vote at 59%, with 10% undecided and 2% saying they will not vote at all.