The three main Westminster political parties have made their latest offer to Scotland to stop them voting for independence - ahead of a television debate that could swing the campaign in favour of the Yes campaign.
Holyrood will get more tax-raising powers and greater responsibility for social security if voters in Scotland reject independence, David Cameron and his Labour and Liberal Democrat counterparts have pledged.
The leaders of the Conservative, Labour and Liberal Democrats have made a formal joint declaration, making clear their commitment to delivering further powers for the Scottish Parliament after the 2015 general election.
The commitment has been made ahead of tonight's televised debate between First Minister Alex Salmond and ex-Labour chancellor and leader of the Better Together campaign, Alistair Darling.
The Yes campaign is hoping Salmond's debating skills will give it the boost it needs ahead of September's referendum.
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The three parties have already set out their own proposals for enhancing devolution, with the three Scottish leaders coming together to promise more powers in the event of a No vote in next month's independence referendum.
Now, Cameron, Labour leader Ed Miliband and Liberal Democrat leader Nick Clegg have all signed a joint declaration which states: "We support a strong Scottish Parliament in a strong United Kingdom and we support the further strengthening of the Parliament's powers."
The three leaders go on to promise to "strengthen further the powers of the Scottish Parliament, in particular in the areas of fiscal responsibility and social security".
The declaration continues: "The Scottish Labour Party, the Scottish Conservative and Unionist Party and the Scottish Liberal Democrats have each produced our own visions of the new powers which the Scottish Parliament needs.
"We shall put those visions before the Scottish people at the next general election and all three parties guarantee to start delivering more powers for the Scottish Parliament as swiftly as possible in 2015.
"This commitment will deliver a stronger Scottish Parliament in a stronger United Kingdom."
Scottish Labour leader Johann Lamont said former first minister Donald Dewar had "united the country when he stood up in 1999 and said 'there shall be a Scottish Parliament'."
She claimed that was an "historic day for Scotland but it was not the last word on devolution", adding: "As people's confidence in the Scottish Parliament has grown, we have looked to strengthen devolution and have worked with others where possible to deliver change.
"So as Donald's successor I am proud to say with certainty - there shall be more powers for the Scottish Parliament.
"The ambition for most Scots is a strong Scottish Parliament with more powers but backed by the security and stability of the United Kingdom - this can be delivered with a No vote on September 18."
Scottish Conservative leader Ruth Davidson told voters: "On September 18, saying No Thanks doesn't mean no change.
"It means we can get on with building a more responsible and a more powerful Scottish Parliament while remaining part of the UK family of nations."
Willie Rennie, leader of the Scottish Liberal Democrats, said: "This statement of common endeavour signed by all the main UK party leaders makes clear our unshakeable commitment to building a stronger Scotland in the UK.
"People can be confident that more powers are guaranteed. A No vote opens the door to change that the majority of people in Scotland wish to see, with a strengthening of the best of both worlds for Scotland."
A spokeswoman for First Minister Alex Salmond said: "No-one in Scotland will be fooled by this Westminster-led rehash of vague promises and unspecified more powers in the event of a No vote - the Tories have tried that before.
"David Cameron fought tooth and nail to keep a more powers option off the ballot paper, so how can anyone take him seriously now?
"The reality is that only a Yes vote on September 18 will give Scotland the powers we need to create a more prosperous and fairer society."