When the "don't knows" were included in the YouGov poll, the Yes to independence campaign was still ahead at 47 to 46.
The figures lit up on social media, unsurprisingly among supporters. But political analysts drew a note of caution about how polling related to how the final result would pan out on 18 September.
The Independent on Sunday's political columnist, John Rentoul, said: "As with any poll, this one will have a margin of error. Usually this would be plus or minus three points on any of the main numbers. So it is possible that nothing has changed since last weekend's YouGov poll, and that these numbers are just more favourable to the Yes campaign as a result of sampling variation. But last weekend's YouGov poll was already more favourable to Yes than previous polls from the same company, so the trend is definitely in the direction of Yes. The best hope of the Better Together campaign is that the apparent breakthrough of the other side will energise its supporters. There is some evidence from other referendums, such as Quebec in 1995, that even a polling lead for separation on the day of the vote can evaporate as people contemplate the seriousness of the change."
He added it was possible to track a trend from the results: "This latest poll seems to show a continuation of a trend from last week, of Labour voters coming over to the cause of independence: 35 per cent of Labour voters now intend to vote Yes, up from 18 per cent a month ago."
Labour, however, seemed unwilling to shoulder the blame, and certainly not former Prime Minister Gordon Brown, who claimed the closeness of the polls was due to dissatisfaction with Conservative policies which had fuelled a feeling among the Scots that breakaway would improve their lives.
"Why has it been difficult to win Scottish votes in support of this principle of sharing that most Scots hold dear?" he said."Many are angry that the Bedroom Tax was imposed upon Scots against their will while at the same time the very wealthy received tax cuts."
Earlier in the day, The Sunday Times' owner Rupert Murdoch had teased the contents of the poll, which he insisted was "reliable", in a series of tweets. With his rarely hidden dislike for the Conservative and Labour leaderships intact, he tweeted: "Scottish independence means huge black eye for whole political establishment, especially Cameron and Milliband [sic]".
The concern at the narrowing polls has led the Better Together campaign to enter cross-party talks to come up with a new offer to Scottish residents in the final passage of campaigning, it was also suggested last night. More reassurances about further devolution of powers from Westminster to Holyrood are set to be put on the table, pledges that would be hardened up in the next Queen's Speech with the conciliatory approach of bringing in SNP members to discuss how a new Scottish "conference" would operate in the wake of a "no vote".
Alistair Darling, who leads the Better Together campaign, said last night: "This [new poll] must serve as a wake-up call to anyone who thought the referendum result was a foregone conclusion."
