Momentum in the run-up to next week's independence referendum is all with the Yes campaign while the "relentlessly negative tactics" of the pro-UK parties "appear to be failing", the Scottish Deputy First Minister has claimed.

Nicola Sturgeon spoke as the campaign for Scotland's future entered its final full week.

Voters north of the border go to the polls on September 18 to decide if the country should remain in the United Kingdom or become independent.

As the campaign entered the last 10 days, Ms Sturgeon was joined on the campaign trail by Leanne Wood, the leader of Welsh nationalists Plaid Cymru.

The pro-independence campaigners were buoyed by a YouGov poll yesterday which put support for Yes ahead for the first time.

When undecided voters are removed from the study, 51% support Scotland leaving the UK, compared to 49% who want to remain in the union.

Another poll by Panelbase also showed a very small gap between the rival campaigns, but this time put No ahead, with 52% supporting a No vote and 48% for Yes.

Ms Sturgeon said: "I don't think there's any doubt at all the momentum is with the Yes campaign but there is no sense of our campaign taking anything for granted.

"We saw one very welcome and encouraging poll yesterday putting us ahead, with another poll still showing us as slightly behind.

"We have campaigned on the basis of patient persuasion, often person by person right across the country, that's what we'll continue to do.

"But there is no doubt, as people come to their decisions, after careful consideration, increasing numbers of people are concluding the best way to protect the health service, create jobs and ensure we never get Tory governments we don't vote for is to vote Yes."

The Deputy First Minister said that as polling day grew closer, increasing numbers of women and Labour supporters were now backing a Yes vote.

"We are seeing in polls the gender gap close, I think that's positive, and Labour supporters increasingly supporting Yes," she said.

"The reason for that is they want the same as I want - greater social justice, the ability to protect our public services, to invest in the health service not nuclear weapons and to be in charge of the decisions that shape our country."

She added: "Independence isn't a panacea, nobody argues that it is a magic wand that is going to pave the streets with gold. We will have our challenges, our ups and downs, as all countries do.

"But we will be in charge of our own resources and the decisions that shape the kind of country we are - that's the big opportunity we've all got next week and I really hope we vote Yes to take that opportunity."

Both Ms Sturgeon and Ms Wood warned remaining in the union could impact on NHS budgets.

They spoke out as nearly 70 healthcare professionals from across Scotland - including hospital consultants, GPs and midwives - signed an open letter backing a Yes vote as the best way to protect the NHS.

Ms Sturgeon, who was speaking outside the Victoria Infirmary in Glasgow, said: "The message today is that if you want to protect the National Health Service then you need to vote Yes, because right now while the Scottish Government has got policy control over the health service we don't control our budget.

"We've seen our budget cut, we know there's more cuts to come and the more the budget is cut the harder it gets for any Scottish Government to protect the things that matter, chiefly the National Health Service.

"We need to marry up that policy control with control over our own resources, that way we can spend our vast resources on the things that matter to us, rather than watch billions wasted on things like nuclear."

The Plaid Cymru leader said she was "delighted" to join in the campaign for Scottish independence.

Ms Wood said: "My message today is simple - a Yes vote is the opportunity of a lifetime for the people of Scotland to start building a fairer and more prosperous society.

"I would urge them to grab the opportunity with both hands."

Alistair Darling, the man leading the fight to keep Scotland in the UK, said he was still ''very confident'' that voters will reject independence.

He insisted the gap between support for the Yes and No campaigns had always been expected to narrow, and dismissed claims that the pro-UK Better Together campaign was now being forced into panic measures to shore up support.

But the snowballing momentum behind the separatists has sent the pound plummeting to a 10-month low of just below 1.62 versus the US dollar and Scotland-based financial institutions have also taken a hit, with Royal Bank of Scotland, Lloyds Banking Group and Standard Life shares falling by more than 2%.

David Cameron, who spent the weekend with the Queen at Balmoral, will attempt to convince sceptics this week that Scotland will get significantly more autonomy even if independence is rejected.

Labour is deploying some of its biggest beasts to try to halt the apparent nationalist surge - with Ed Miliband also stressing that extra powers will start being devolved ''right after'' a No vote.

Mr Darling dismissed suggestions that plans to outline the handover of more powers this week were little more than a bribe.

He told BBC Radio 4's Today programme: ''The additional powers coming to the Scottish Parliament were announced by the party leaders north and south of the border some time ago.

''People have said yes, we want to know the timetable and the process, and that is something that the Government is going to announce this week.''

He added: ''I have always said that the polls will narrow because this is a huge debate. We are seeing record amounts of people registering to vote.''

Mr Darling said voters were ''very alive to the risks'' in breaking away, particularly the uncertainty over the currency.

''I believe that we will win this referendum because a majority of people in Scotland do want to ensure that there is a better and stronger future for themselves and the generations to come,'' he said.

''I'm very confident we will win the day.''

Writing today, Tory Mayor of London Boris Johnson made an emotional appeal to keep the UK together, warning that Scottish independence would be ''an utter catastrophe for this country''.

''We will all have lost a way of thinking about ourselves, a way of explaining ourselves to the world,'' he wrote.

''We are on the verge of trashing our global name and brand in an act of self-mutilation that will leave our international rivals stunned, gleeful and discreetly scornful.''

David Cameron's official spokesman confirmed that the Prime Minister intends to visit Scotland ahead of referendum day, but was unable to give details of any trips north of the border by the Premier or other ministers this week.

The spokesman told a regular Westminster media briefing: "I doubt there are many in the UK who are unaware of the Prime Minister's approach and the strength of his views. He himself has been making visits to Scotland, where he has been setting out that case very regularly, including on a couple of occasions last month.

"He will be there again soon."

Asked why the Prime Minister had not cleared his diary to fight for the Union in the last days of the campaign, the spokesman said: "What he will be doing is continuing to make the case and make the argument strongly in the way that he has, alongside the other voices that are making the case."

He insisted that the Government was still making no contingency plans, in the wake of opinion polls suggesting the Yes campaign is gaining ground.

"No, there has been no change," he told reporters who asked whether work was under way in Whitehall on arrangements for dealing with a Yes vote. "The Government's entire focus is on making the case for the UK staying together and Scotland remaining part of the United Kingdom.

"That is what the Government's entire focus is going to be between now and referendum day."

The spokesman said that details of a proposed plan to devolve more powers to Scotland in the event of a No vote would be released by the three main UK political parties, rather than by the Government.

He said this was in line with the approach taken when Mr Cameron, Ed Miliband and Nick Clegg signed a joint declaration as party leaders last month, promising that Scotland would be granted more powers over tax and social security if voters reject independence. This week's announcement is expected to flesh out the timetable for this plan, rather than extending the parameters of the offer.

Deputy Prime Minister Nick Clegg said the announcement expected later this week would set out a consensual process for devolving "far greater powers", similar to 2009's Calman Commission, resulting in a new settlement for Scotland.

Speaking at a Westminster press conference he said: "It is not in the gift of the three main parties to impose from on high a new devolution settlement on the people of Scotland, that would be wholly wrong."

He added: "What will be discussed or announced later this week is really about the process of and the timetable by which that consensual arrangement can unfold, leading as quickly as possible to new powers being enjoyed by the Scottish Government in what is, then, a new settlement which I think reflects what a lot of Scottish people tell me is what they want, which is ... far greater powers for Scotland but within the security and stability that the family of nations in the United Kingdom provides."