THE referendum battle enters a dramatic final month today as Alex Salmond launches a last push for votes buoyed by polls showing the Yes campaign gaining ground.

The First Minister will take his Scottish Government cabinet to Arbroath where he will use the symbolic venue to issue a "Declaration of Opportunity," casting independence as a once-in- a-lifetime chance to "build a more ­prosperous and fairer Scotland".

The visit, amid a flurry of campaign activity by both sides, comes after two weekend polls suggested the Yes campaign has made headway over the past month.

An ICM survey showed the No campaign's lead drop to 10 points, when undecided voters were excluded, while a Panelbase poll for Yes Scotland put the gap at just four points, discounting the don't-knows.

In another boost for the Yes camp, distinguished historian Sir Tom Devine yesterday revealed his support for independence.

Today Mr Salmond will seek to put the future of Scotland's devolved health service at the heart of his case for a Yes vote.

In a move described as desperate by the No campaign, he will repeat his fiercely disputed claim that NHS Scotland's budget is under threat from knock-on effects of privatisation in the English health service. Douglas Alexander, Labour's shadow foreign secretary, said yesterday voters "will not be fooled" by Mr Salmond's remarks about the health service.

Ahead of the visit, the Yes campaign yesterday attempted to draw a line under the row over an independent Scotland's currency that has dogged the First Minister since his bruising encounter with No campaign leader Alistair Darling a fortnight ago.

In a radio interview yesterday, Mr Salmond said he wished he had explained his proposal for a currency sharing deal "in more detail".

But Yes Scotland released further findings from its Panelbase poll suggesting relentless pressure on Mr Salmond had not delivered a killer blow to his hopes of winning next month.

Rather, it showed the UK parties' decision to rule out the First Minister's plan had made slightly more people (28 per cent to 25 per cent) more likely to vote Yes than No.

According to the poll, 56 per cent of voters also believed a formal currency union would be in the best interests of an independent Scotland and the rest of the UK, despite expert warnings such a pact would quickly collapse.

Deputy First Minister Nicola ­Sturgeon said: "The poll shows the bullying of the Westminster parties continues to backfire. The No campaign's supposed trump card has indeed turned out to be a bluff."

Mr Salmond will view a copy of the 1320 Declaration of Arbroath, a statement by Scots nobles of their freedom from English rule, during his visit to the town's abbey today. Looking ahead to September 18, he will say: "Those of us lucky enough to cast our votes on that day are truly a privileged generation: perhaps the most privileged in this nation's history.

"The opportunity we have isn't unique, but it is very precious. We have the chance to take power out of the hands of the Westminster elite and into the hands of the people of Scotland."

But Mr Salmond's allegation Scotland's devolved NHS is under threat as a result of decisions in England, where health service funding continues to rise, was criticised by Mr Alexander.

He said: "These ever more desperate claims seem motivated more by saving their campaign than saving the NHS. All of us know the NHS is devolved in Scotland and is the responsibility of the Scottish Government."

Commenting on the polls, the Paisley MP, who will mark the month-to-go milestone at a Better Together campaign event in Glasgow today, added: "The remarkable thing over the last two years of campaigning has been how little public opinion has changed.

"We started the campaign speaking for the majority of Scots and now, as we enter the final month, we still speak for that majority.

"Not a single independently commissioned poll has ever shown Yes in the lead.

"The challenge for our campaign is to turn the majority of support into the majority vote on September 18. My message to everyone that supports our campaign is this: 'If you want it, you have to vote for it.'"

Both sides are poised to step up their efforts in the days ahead.

Better Together, the lead pro-UK group, will tonight air its first referendum broadcast on BBC and ITV.

The first of four such broadcasts by each side, it will feature ordinary people explaining why they are voting No.

The campaign also revealed plans to contact every household in Scotland at least three times over the next four weeks, targeting all postal voters individually. It also claimed it would put 25,000 activists on the ground.

The pro-independence Scottish Greens, meanwhile, revealed plans to leaflet 500,000 homes between now and polling day.