The value of the pound has fallen in the wake of an opinion poll which suggested the pro-UK campaign had lost its lead ahead of the Scottish independence referendum.

Sterling fell by about 1.3% against the US dollar to a 10-month low of $1.61.

Shares in some firms with Scottish links have also fallen.

The SNP has dismissed a promise by the Chancellor to unveil a timetable for further devolution if voters reject independence as a last-minute "bribe".

George Osborne had said on Sunday that a "plan of action" would be set out in the next few days to give "more powers to Scotland; more tax powers, more spending powers, more powers over the welfare state".

BBC Scotland's political correspondent Glenn Campbell has reported that a new body will also be set up to hammer out more powers for Holyrood if there is a "No" vote on 18 September.

It came in the wake of a YouGov poll for the Sunday Times over the weekend which was the first mainstream study to put the pro-independence Yes Scotland campaign narrowly ahead.

In other developments:

Former prime minister Gordon Brown has set out his own timetable for boosting the Scottish Parliament's powers in the event of a vote against independence. Downing Street said it was "content" with the proposed timetable.

Shadow chancellor Ed Balls has pledged to "oversee a further and big transfer of financial powers from the Treasury to the Scottish government" under any future Labour government

Deputy First Minister Nicola Sturgeon is set to argue that a 'Yes' vote is the only way to save the NHS in Scotland

Nobel Prize winning economist Paul Krugman has written an article on Scottish independence for the New York Times in which he warns that the "risks of going it alone are huge". He also claims: "You may think that Scotland can become another Canada, but it's all too likely that it would end up becoming Spain without the sunshine."

Buckingham Palace has insisted the Queen remains neutral, despite a number of newspapers reporting her apparent concern about the potential break up of the United Kingdom

The poll of 1,084 people, carried out between 2 and 5 September, suggested that, of those who have made up their mind, 51% planned to back independence, while 49% intended to vote no.

On Monday morning, shares in Scottish-based firms dominated the top fallers on the stock market.

Edinburgh-based Standard Life fell 3%, Royal Bank of Scotland slipped 2.4% and Lloyds Banking Group, which owns Bank of Scotland and Scottish Widows, dropped 2.7%. Their share prices recovered slightly later in the day but remained in negative territory.

Perth-based energy supplier SSE, Glasgow pumps specialist Weir Group and fund manager Aberdeen Asset Management also all fell between 1.5% and 1.9% early in the day and were still down by the end of trading.

Alistair Darling, head of the pro-UK Better Together campaign, told BBC Radio 4's Today programme that the referendum race was "clearly very tight" but said there was no panic.

He added: "We are in a position now where every voter in Scotland could potentially tip the balance in the referendum.

Media playback is unsupported on your device Media caption Alistair Darling: "Every voter in Scotland could now potentially tip the balance in this referendum, but I am confident that we will win"

"But I am confident we will win because we do have a very strong, positive vision of what Scotland can be, both in terms of the opportunities and the security that come from being part of the UK, a strengthened Scottish Parliament, with more powers which is what people want and you can do that without having to break up the country to do it."

Mr Darling stressed that no new powers would be put on the table beyond those already announced by the three main Westminster parties earlier this year.

He added: "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 the government is going to announce this week.

"But remember this, this is a referendum on whether or not we stay on the United Kingdom. It is not a referendum on what further powers we are going to get. We are going to get them anyway, if we stay in the United Kingdom.

Analysis: Brian Taylor, BBC Scotland political editor

It may not be outright panic. But it is hardly calm, measured insouciance either.

Better days may - or may not - return for Better Together but, right now, it is scarcely glad confident morning.

The reason? TOP, that opinion poll. You know, the one by YouGov in the Sunday Times which suggested that the "Yes" campaign might win this referendum.

At the core of the Better Together campaign, a series of interlinked challenges.

Firstly, they are seeking to negate a proposition, that of independence. They are saying "No". They are advocating a "No" vote.

The challenge is to say "No", positively. To project an upbeat vision of the continuing and reformed Union while talking up the downside of independence.

Secondly, they may be Together - but they are scarcely chums. Indeed, Labour, the Liberal Democrats and the Tories will soon be clutching each warmly by the throat in the UK General Election.

That creates a temptation to diss their comrades as well as their opponents.

Labour leader Ed Miliband has joined Mr Osborne in saying the process of handing more powers to Scotland should begin immediately after any "No" vote.

SNP leader Alex Salmond said it was a "panicky measure" announced without credibility because his Yes Scotland campaign was "winning on the ground".

Neither Prime Minister David Cameron nor any other Conservative Cabinet Minister is expected to visit Scotland this week, but Downing Street denied any suggestion of complacency over the referendum result.

Media playback is unsupported on your device Media caption Scottish Finance Secretary John Swinney says there is an "atmosphere of absolute panic in the no campaign"

A spokesman for Number Ten was also unable to give any details of when an announcement would be made on setting up a new body to agree a timetable for handing more powers to Scotland. He said this would be an issue to be settled by the political parties.

It is understood discussions are still going on between the three main parties to finalise the details.

Number Ten also confirmed that no contingency plans are being put in place for a possible "Yes" vote in the referendum.

Scottish Finance Secretary John Swinney told the BBC that it was a fair assessment of the polls to say the Yes campaign remained behind in general, but said his experience was that undecided voters were moving to Yes by a factor of two to one.

He added: "The movement is in our favour and the campaign is exciting an enormous amount of interest and activity and participation on the ground across Scotland. I think it is the formidable strength of the 'Yes' campaign that is motivating that."

Analysis: Nick Robinson, BBC political editor

On the morning after the poll before, "Vote No and get something better" summed up George Osborne's message. It's a tried and trusted message which worked in the independence referendum in Quebec when a last minute poll lead for Yes was transformed into a narrow No. It is, though, a message with a difficult history in Scotland.

Thirty five years ago it was precisely what Scots were told when they were voting in a referendum on a much more modest proposal - to create a Scottish Parliament with some devolved powers.

A former prime minister, a Scot and, as it happens, a Tory, Sir Alec Douglas Home urged his countrymen to vote No and get "something better". What they got soon afterwards was 18 years of Margaret Thatcher's government and no devolution at all (until, that is, Labour were re-elected in 1997).

That is just one reason why Osborne's promise of a plan to transfer new powers to Holyrood - covering tax raising, spending and benefits - caused such confusion yesterday. It is why Alex Salmond felt able to attack it as a sign of "panic" on the No side.

The other reason is that the three rival Westminster parties - the Conservatives, Labour and Liberal Democrats - have not agreed a plan for which precise powers to devolve. Each party has published its own set of proposals which overlap in the areas Osborne listed.

Read more from Nick

Referring to Mr Osborne's announcement, Mr Swinney said: "There is nothing new being offered this week. We may well get a timetable but the substance, the actual powers, the things that matter, Alistair Darling made absolutely crystal clear yesterday in contradicting George Osborne, that on the substance there will be absolutely nothing new.

"If I look at the different offering of the the Labour party, the Liberals and the Conservatives they are all different. I can't answer to you today, neither could Alistair Darling, what would be the proposition that people get under this alternative scenario? So it is vague and it has all been offered before.

"The second point is that in 1979 Scotland was told vote 'No' in the referendum and you'll get a stronger parliament and what we got was a Conservative government for 18 years that we never voted for, industrial devastation and no parliament.

"So I think the moral of the story of recent history in Scotland is if you want a guarantee of strong powers for the Scottish Parliament you have to vote 'Yes' in the referendum a week on Thursday."

Canon Kenyon Wright, who chaired of the Scottish Constitutional Convention that paved the way for the creation of the devolved Scottish Parliament in 1997, said Mr Osborne's announcement had a "whiff of desperation about it".

Canon Wright, who now supports independence, added: "It's now clear that devolution has two main problems. One is that it is incomplete and will never cover the areas needed to protect the people of Scotland on issues like welfare. The second is that it is insecure and always will be, so long as sovereignty remains at Westminster."

Image copyright PA

BBC political correspondent Ben Wright said the outcome of the referendum now looked "utterly uncertain".

He said the "sleepy assumption" in Westminster among the pro-Union parties that there would be a relatively comfortable vote against independence had been completely destroyed over the past few days.

Voters in Scotland go to the polls on Thursday 18 September, when they will be asked the "Yes/No" question: "Should Scotland be an independent country?"

In the last full week of campaigning, Mr Miliband is expected to be joined on the stump by Gordon Brown.

The former Labour prime minister has said Westminster must deliver on its promise of further devolution so "a No vote doesn't mean nothing happens".

A YouGov poll for the Sunday Times over the weekend was the first mainstream study to put Yes Scotland narrowly ahead.

The poll of 1,084 people, carried out between 2 and 5 September, suggested that, of those who have made up their mind, 51% planned to back independence, while 49% intended to vote no.

The cross-party Better Together campaign had previously retained a lead in polls, often reaching double digits.

In London, the Tory mayor Boris Johnson said Scotland going independent would be "an utter catastrophe".

"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," he wrote in the Daily Telegraph.

What are the No parties offering?

Image copyright Getty Images

Scottish Labour - Its devolution commission has backed increased tax-varying powers and control over some elements of welfare and benefits policy. It said MSPs should be able to vary tax by up to 15p, giving them the option of restoring the 50p rate for top earners - but there would be no power to cut the upper income tax rate, which currently sits at 45p.

Scottish Conservative - Scottish Conservative leader Ruth Davidson has said Scotland should be given full income tax powers, a key recommendation of the party's devolution commission, chaired by Lord Strathclyde. The commission, which said the income tax plan would see the Scottish Parliament accountable for 40% of the money it spent, also said there was a case for a share of Scottish VAT receipts being assigned to Holyrood.

- Scottish Conservative leader Ruth Davidson has said Scotland should be given full income tax powers, a key recommendation of the party's devolution commission, chaired by Lord Strathclyde. The commission, which said the income tax plan would see the Scottish Parliament accountable for 40% of the money it spent, also said there was a case for a share of Scottish VAT receipts being assigned to Holyrood. Scottish Liberal Democrats - Its commission, chaired by former UK party leader Sir Menzies Campbell, proposes a federal structure for the UK. It would give the Scottish Parliament control over financial powers including inheritance tax, capital gains tax, income tax and a good share of corporation tax. It also called for the devolution of new borrowing powers; new Partnership Powers to require Holyrood and Westminster to work together; a role for the Supreme Court in resolving disputes; and a new needs based formula to eventually replace the Barnett Formula.

And over the weekend the leader of the pro-Union Better Together campaign, Alistair Darling, clarified that the chancellor's announcement was "about the process and timetable" for more devolution, not new powers.

The UK government said the timetable for new powers for Scotland would not break rules on what can be discussed during the referendum period.

What are the issues of the referendum?

Image copyright SPL

As the people of Scotland weigh up how to vote in the independence referendum, they are asking questions on a range of topics.

Elsewhere, Mr Miliband will on Monday thank trade unions at the TUC general dinner in Liverpool for their work on the Better Together campaign.

He will say the unions have signed a joint statement, "declaring that our strength comes from staying together and that separation would damage the rights and conditions of working people".