MORE undecided voters came out for No than Yes after the historic STV debate between Alex Salmond and Alistair Darling, new poll figures have revealed.

The breakdown from a snap post-debate survey showed that of the 14 per cent of people unsure how they would vote in the referendum at the start of Tuesday night's programme, 33 per cent backed No afterwards while only 16 per cent made up their minds to support Yes.

Most of the don't-knows (51 per cent) remained undecided after the two hours of intense debate between the SNP leader and the head of Better Together.

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The figures emerged from an ICM/Guardian survey conducted in the immediate aftermath of the debate as both sides continued to claim victory.

Blair Jenkins, chief executive of Yes Scotland, claimed his campaign was "winning decisively" among undecided voters after more of the don't knows said Mr Salmond had won the debate, even if he failed to convince large numbers to back independence on the night.

Mr Jenkins also cited figures showing a rise in support for Yes among women and older voters.

He said: "We are winning where it matters, and I am extremely confident we will achieve the small swing now required to achieve a Yes majority on 18 September."

After weighting to make the sample representative of the population at large, ICM's panel of 512 people who gave their instant verdict on the debate comprised 40 per cent Yes supporters, 46 per cent in favour of No and 14 per cent who were undecided.

Asked their voting intentions after the debate, support for Yes rose two points to 42 per cent; No was up one point to 47 per cent and the don't-knows fell to 13 per cent.

The No side held on to 92 per cent of its support, with six per cent swapping sides to Yes and two per cent becoming undecided. Yes kept 90 per cent of its support. Among Yes supporters at the start of the night, two per cent switched sides to No while eight per cent said they were undecided at the end.

Responding online, panel members were asked to judge the winner of the debate based solely on the exchanges on the studio.

Overall, 47 per cent said Mr Darling won, 37 per cent felt Mr Salmond came out on top and 15 per cent were unsure.

Stripping out the don't-knows, the poll gave Mr Darling victory by 56 per cent to 44 per cent.

The Yes campaign took comfort yesterday from figures showing Mr Salmond won the debate according to people who were undecided about independence at the end. Among that small but important group, 40 per cent said Mr Salmond triumphed, 14 per cent called it for Mr Darling while 46 per cent were undecided.

Stripping out those unsure of the result, 74 per cent said Mr Salmond won, compared with 26 per cent who called it for Mr Darling.

Among those undecided at the start of the night, 55 per cent felt Mr Salmond won compared with 45 per cent preferring Mr Darling.

Polling expert Professor John Curtice, from Strathclyde University, said both leaders had failed to convince undecided voters to back their side.

In a BBC interview he said: "I don't think there was a clear winner. The evidence of the ICM poll is that for the most part Yes supporters thought Alex Salmond had won, No supporters for the most part thought Alistair Darling won.

"The undecided were fairly evenly divided, with maybe a slight edge for Mr Salmond. That suggests, frankly, neither side secured decisive advantage."

He added: "I'm not surprised at the polling evidence. It wasn't clear that either of them used the debate to reach out effectively to the undecided and the uncommitted voters.

"They both led on the issues that mattered to their existing supporters, not necessarily the subjects that are central to undecided voters."

Mr Darling yesterday met staff at Glenrothes-based Fife Fabrications, which employs 80 people, and is backing the No campaign because of concerns over the currency of an independent Scotland.