Bank of England Governor Mark Carney today repeated his view that a currency union between an independent Scotland and the remainder of the United Kingdom would be incompatible with sovereignty.

Carney, speaking at a conference of trade union leaders, recalled a speech he made in January in which he said a successful currency union would require cross-border agreements on tax and spending as well as on banking rules.

He also noted the opposition of Britain's three main political parties to a currency union with an independent Scotland, as proposed by the Scottish nationalists.

"So it's in that context, if you put it together, a currency union is incompatible with sovereignty."

A spokesman for Finance Secretary John Swinney said: "Governor Carney made a full statement back in January on the arrangements that would be required to establish a successful currency union - including reaching shared agreements on certain elements of sovereignty such as overall debt levels.

"All of these issues were considered in detail by the Fiscal Commission, which includes two Nobel Laureates, and concluded that a currency union was in the best interests of both an independent Scotland and the rest of the UK.

"The Governor has made clear that the bank is ready to implement whatever is decided.

"Successful independent countries such as France, Germany, Finland and Austria all share a currency - and they are in charge of 100% of their tax revenues, as an independent Scotland would be. At present under devolution, Scotland controls only 7% of our revenues."

Meanwhile, the City regulator has told MPs it has put contingency plans in place if Scotland votes in favour of independence.

John Griffith-Jones, chairman of the Financial Conduct Authority (FCA), warned that the process of putting a new regulatory regime in place if Scotland votes Yes in the independence referendum is likely to involve some "complicated" decision-making.

He said: "We have done some basic contingency planning, although it's fair to say that we think that the conduct issues are likely to emerge slowly once we know what the Scottish Parliament, if the vote was Yes, actually want to put in place."

He said the FCA is doing "such things as making sure that our phone lines are properly manned if people ring us... making sure we have a position around what advice would be appropriate to be given on day one, were consumers to ask: 'What should I do?'"

Asked by MPs sitting on the Treasury Committee if a new regulator would need to be put in place in the event of Scotland deciding to break away from the rest of the UK, Mr Griffith-Jones said: "It would be the responsibility of the Scottish Parliament to decide how they want to do regulation."

Asked if setting up a new regulator would be a straight-forward job, Mr Griffith-Jones replied: "I think it'll turn out to be complicated to work out the detail, but until we have a discussion... obviously there are simple ways for them to do it and more complicated ways."

He said that the "detailed work" on how a new regulator would work "needs to be started once you know what the Scots actually want".

The FCA chairman later added: "I think we're going to find ourselves with a lot of work to do... in the process of setting up a new regulatory regime."

With Scotland positioned as a major provider of financial services, some commentators have highlighted evidence of consumer uncertainty over exactly what Scottish independence would mean for their financial arrangements.

There has been speculation that this nervousness could prompt a flight to safety, with some people deciding to move their money south of the border.