Alex Salmond will face renewed pressure on currency and economic prospects for an independent Scotland on Monday in his second referendum debate with Alistair Darling, leader of the pro-union campaign.
Independence activists have been cheered by opinion polls that suggest the pro-union lead is narrowing, despite an underwhelming performance by Scotland’s first minister in his last clash with Mr Darling.
The head of the “Better Together” campaign is expected to seize on claims that the nationalists have been overstating likely future North Sea oil revenues and to focus heavily on uncertainty about the currency an independent Scotland would use.
Mr Salmond’s Scottish National party insists that the country would be able to form a formal currency union with the remaining UK, despite the rejection of this proposal by all three main Westminster parties.
The SNP’s position is offered some support on Monday by a report from Fiscal Affairs Scotland, a think-tank, that says objections outlined by the Treasury’s senior civil servant in February could all be overcome.
However, John McLaren, the think-tank’s executive director, said the compromises required could leave Scotland with little control over monetary and fiscal policy.
“To some this may seem at odds with the needs of an independent Scotland, as well as the rationale for it,” Mr McLaren said.
Pro-union politicians insist that formal currency union would be impossible, an independent currency would be risky and difficult to introduce and informal use of the pound – or “sterlingisation”, which has been identified by Scottish government advisers as a possible stopgap arrangement – would be disastrous for the financial sector.
Ed Balls, the shadow chancellor, said on Sunday that a formal currency union was “off the table”.
"I fear that an independent Scotland would end up finding that joining the euro would be the least worst of all the bad options," Mr Balls told The Observer newspaper.
SNP strategists wave aside suggestions that Scotland would have to adopt the euro, noting that even if it was required to commit in principle, as a condition of EU membership, there is no mechanism for forcing adoption of the currency.
Mr Salmond, a former energy economist, is also likely to respond to criticism that he has overstated oil and gas revenues Scotland could expect by citing industry estimates that up to 24bn barrels of oil could still be extracted from the North Sea.
Sir Ian Wood, former head of oil services supplier Wood Group and one of the Scottish energy sectors most respected figures, said last week that even with more sympathetic tax and regulation, the likely best outcome was “between 15bn and 16.5bn barrels”.
However, industry body Oil and Gas UK has said it “remains of the view” that up to 24bn barrels could be recovered if appropriate policies were adopted.
Alex Kemp, an expert on Scottish oil, said an estimate of 15-16.5bn barrels did not take into account the potential for more developments after 2050, which made the 24bn figure appear “plausible”.
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