By Adam Bienkov
George Osborne has been accused of making "fantasy promises" to Scottish families after claiming that they will be £2,000 better off if they vote to remain in the UK.
In a speech tomorrow to oil industry executives in Aberdeen, the chancellor will argue that a new border between Scotland and England would dramatically slow growth north of the border.
He will also claim that average incomes would rise by an additional four per cent if Scotland votes to reject independence.
"Replacing the current relationship between Scotland and the rest of the UK with a relationship similar to that of euro area member states would create significant headwinds to Scottish growth" Osborne is expected to say.
Osborne's visit comes as a new poll suggests that the campaign for Scottish independence is faltering.
The poll conducted by YouGov found that 59% of Scots are now opposed to independence for Scotland with just 29% in favour.
The chancellor is expected to release a new report claiming that Scottish independence would dramatically reduce trade between Scotland and the rest of the UK.
The report cites evidence from neighbouring US and Canadian states, where trade is thought to be 44% lower than it would be without a border.
Campaigners against independence urged voters not to risk killing off growth in Scotland.
"If we didn't already have the single UK market we would create it, so it makes absolutely no sense to put up barriers with businesses and customers in the rest of the UK," a spokesperson for the Better Together campaign said.
"Being part of the UK allows Scottish businesses to thrive and provides greater opportunities than we would have if we went it alone. Why on earth would we want to put this at risk for the sake of Alex Salmond's obsession with independence?"
The Scottish government strongly disputed the chancellor's claims, saying that the coalition's austerity policies would actually make families £1800 a year worse off.
Deputy first minister Nicola Sturgeon accused Osborne of making "fantasy promises" to voters.
"The Tories are trying to take the people of Scotland for fools if they think families facing real hardship will buy fantasy promises from George Osborne."
"As an independent country, in a single market not just with the rest of the UK but with the European Union - a position threatened by Westminster - we will finally be able to make our own decisions, to support our key industries, our workforce and to counteract the economic imbalance caused by London-based economic policy," Sturgeon said today.
Sturgeon also suggested that the "deeply unpopular" chancellor was the wrong person to make the case against independence for Scotland.
A poll earlier this year found that public support for the government's economic policies plummets when voters are told that they belong to George Osborne.
Other polls have shown that up to three quarters of Scottish voters believe that Osborne is doing a bad job as Chancellor.