The governor of the Bank of England is to intervene in the row over what currency an independent Scotland would use.
Mark Carney is expected to address the issue of currency union when he makes a speech in Edinburgh today.
He has already met Scotland's First Minister Alex Salmond for talks - the first time the two men have had face-to-face discussions since Mr Carney took over as Bank of England governor in July last year.
The Scottish Government has already put forward plans for Scotland to retain the pound if the country votes for independence in September's referendum, establishing a "sterling zone" with the rest of the UK.
UK ministers including Chancellor George Osborne have previously cast doubt on whether this is achievable, saying it is unlikely the UK Government would back such a move.
But Mr Salmond said yesterday that Mr Carney's predecessor at the Bank of England, Sir Mervyn King, had suggested the Treasury could change its approach in the event of a Yes vote.
The First Minister told how he met Sir Mervyn " a couple of years back", and added: "The first thing he said to me was, 'your problem is what they say now', meaning the Treasury, 'and what they say the day after a Yes vote in the referendum are two entirely different things'."
Mr Carney has already warned of "challenges" in adopting a shared currency without having "certain institutional structures" in place, telling the BBC l ast week there were " issues with respect to currency unions".
He said: "We've seen them in Europe. It's one of the factors that affects, actually, the outlook for the UK economy, has affected us over the last five years, affects us going forward, the challenges of having a currency union without certain institutional structures."
A spokeswoman for Mr Salmond said yesterday that Scottish Government officials had already had "technical discussions" with counterparts at the Bank of England, adding these had assisted the Fiscal Commission that ministers established with its work "including the publication of their report on a macro-economic framework for an independent Scotland, which includes proposals for a shared sterling area".
She added: " The First Minister met with the previous governor of the bank, Sir Mervyn King, before and after those technical discussions - and he looks forward to meeting the new governor tomorrow."
A spokesman for the pro-UK Better Together campaign said : ''What a remarkable coincidence. Just hours before the visit of the current governor of the Bank of England, Alex Salmond makes a claim about something that may or may not have been said by Mark Carney's predecessor. In a double coincidence, this alleged conversation backs up Alex Salmond's arguments."