Two SNP veterans have criticised the present leadership's plan for a currency union with the remainder of the UK if Scotland votes for independence.

Former SNP deputy leader Jim Fairlie said an independent currency is a "prerequisite" of full national sovereignty.

Former SNP leader Gordon Wilson suggested the party's plan to keep the pound could leave Scotland tied to a UK economy which is "dominated" by London and the south east, at the expense of the northern regions.

Meanwhile, Scottish Socialist Party leader Colin Fox, a Yes Scotland board member, has also argued that a "sterling zone" would leave a considerable amount of control over Scotland's economy in London.

Mr Fairlie said a separate currency "is the only option which will allow a Scottish government the degree of economic control necessary to diverge from the history of mismanagement of the Scottish economy since the end of World War II".

"If sovereignty means anything at all to the Scottish people, control of their own currency is a pre-requisite," he said.

Mr Wilson said: "If there is to be any economic advantage with independence, it is to ensure that we have all the tools to manage its economy differently from the Union.

"The elephant in the room is the domination of the UK economy by London and the south of England. Increasingly, under the Union, that is where the prosperity, the increasing population and the political clout are to be found."

Mr Fox said: "It goes without saying that keeping the pound or establishing a 'sterling zone' means handing over a considerable amount of power and control over Scotland's economy and spending options to the Bank of England and the City of London."

A separate currency "seems to make most sense" and is also the option favoured by the pro-independence Green Party, according to Mr Fox.

Members of the pro-union campaign said the comments point to "chaos" within the independence camp.

Better Together campaign director Blair McDougall said: "The poll at the weekend showed that people do not find the case being put forward by the SNP for independence convincing.

"I'm not sure that public bickering and briefings to the media will change that. The nationalists are turning on each other as Scots turn away from independence."

Conservative deputy leader Jackson Carlaw said: "People look at this currency debate and wonder why Scotland would even bother forcing this situation through breaking up Britain when we are already in a successful sterling currency zone called the United Kingdom."

Liberal Democrat leader Willie Rennie said: "If this is the chaos inside the camp, how do undecided voters looking on from outside have a hope of deciphering what Scotland stands to lose on currency if it left the UK?"

SNP MSP Annabelle Ewing said: "The pound is Scotland's currency every bit as much as it is the rest of the UK's, and Scottish Government policy for a formal sterling area post-independence is clear.

"At present, Scotland only controls 7% of all the revenue generated here, and this would go up to just 15% under the terms of the Scotland Act - one of the great benefits of independence is that we would have access to and control 100% of the revenue raised in Scotland, so that we can design tax and economic policies that are right for Scotland.

"The No campaign wants to leave control of the fiscal and economic levers in George Osborne's hands.

"Up until just a few weeks ago the anti-independence parties were insisting that an independent Scotland would have no option but to use the euro, and that scare story has been comprehensively rebutted.

"Only a week ago Alistair Darling was telling us that nothing George Osborne says has got much credibility - yet he is acting as the Tory Chancellor's chief spokesperson in Scotland."