David Cameron is to tell voters there could be “no going back” if they chose to “break up our family of nations”.
The Prime Minster will use his final campaign visit on Monday to issue the warning to waverers.
The latest polling continues to suggest the contest remained too close to call, with several showing a slim lead for the No camp and one suggesting the pro-independence side had a lead of eight points - the reverse of the picture in a poll commissioned by Better Together.
No leads by 50.6 per cent to 49.4 per cent according to Panelbase for the Sunday Times and - with undecideds taken out - by 53 per cent to 47 per cent in research by Opinium for the Observer.
An ICM poll for the Sunday Telegraph put Yes camp in front by 54 per cent to 46 per cent, although it had a smaller than usual sample size of 705.
And a Survation poll commissioned by Better Together found that 54 per cent plan to vote No while 46 per cent intend to say Yes, factoring out undecided voters.
Despite the narrow differences, the leader of the Better Together campaign, Labour former chancellor Alistair Darling, sounded a significantly optimistic tone about chances of a rejection of independence.
“We will win, be in no doubt about it. I know, because I see them every day, our returns are good,” he told the Observer.
On the campaign trail, an equally upbeat Mr Salmond said: “What matters is what’s happening in the streets and communities around Scotland.
“The Yes side has the momentum and that’s going to carry us through next Thursday and that’s because we’ve got a positive message, we want to build a more prosperous economy and a fairer society, and there’s no scare story that the No campaign can mobilise which competes with that positive vision for the future of Scotland.”
Mr Cameron will make what No 10 said was his 10th visit north of the border this year, and is expected to tell voters: “This is a decision that could break up our family of nations and rip Scotland from the rest of the UK.
“And we must be very clear. There’s no going back from this. No re-run. This is a once-and-for-all decision.
“If Scotland votes yes, the UK will split, and we will go our separate ways forever.”
He will say it is not a question about “ whether Scotland is a nation”.
“Scotland is a proud, strong, successful nation. The vote on Thursday is about two competing visions for Scotland’s future.
“The Nationalists’ vision of narrowing down, going it alone, breaking all ties with the UK. Or the patriotic vision of a strong Scottish nation allied to the rest of the United Kingdom with its own stronger Scottish Parliament at its heart and with the benefits of UK co-operation on jobs, pensions, healthcare funding, the currency, interest rates.”