The news came as Edinburgh-based Lloyds, which owns Bank of Scotland, revealed it has finalised contingency plans which could see it quit Scotland in the event of a Yes vote.
It looks increasingly likely that using the pound without agreement from the UK is the SNP’s favoured option if a formal currency union is rejected.
But yesterday Olli Rehn, who stood down two months ago as European Commissioner for Economic and Monetary Affairs, warned the absence of a central bank would block Scotland’s hopes of joining the European Union.
“This would simply not be possible,” he warned in a letter to Westminster Treasury Secretary Danny Alexander.
But Mr Rehn’s claims were rejected by Alex Salmond. He said: “What you require in terms of EU membership is a conduct authority and financial institutions and we’d form these financial institutions as we’ve stated.”
The SNP wants to keep the pound in a formal currency union with the UK, which would see the Bank of England remain as Scotland’s lender of last resort.
Scotland’s financial giants are known to be concerned about “sterlingisation” amid concerns they may be left in the lurch in the event of another major crash.
Banking industry sources said last night Lloyds executives are considering having the group’s registered office in London, with Bank of Scotland operating from Edinburgh as a foreign division. Lloyds has warned independence would affect it in terms of funding, taxes and compliance costs.
However, in a statement, the bank said: “There will be a period between the referendum and the implementation of separation, should a Yes vote be successful, that we believe is sufficient to take any actions we believe necessary.”