THE First Minister of Wales has warned that the principality would try to block attempts to create a currency union between an independent Scotland and the rest of the UK.

Labour's Carwyn Jones claimed in a speech to Edinburgh University last night that the SNP's plan to share the pound and Bank of England within a common sterling zone would put Welsh taxpayers at risk.

Mr Jones insisted that trade and currency lay at the heart of the "positive case" for the Union. He issued a stark warning for his opposite number at Holyrood, Alex Salmond, saying: "If one part of the currency union decides to leave, then that is a matter for them.

"But if an independent nation wants to join, then that is a matter for the people of Wales, Northern Ireland and England - and as the First Minister of Wales, I would want the right to have a say."

The Welsh Assembly member claimed it was "highly unlikely that currency union without strong fiscal controls could work".

The eurozone-style arrangement, he warned, would create uncertainty and slow down economic decision making.

Referring to the taxpayer-funded ­bail-out of RBS and HBOS after the 2008 banking crisis, he added: "The risk to Wales and Northern Ireland would be far greater, so it would only be right for the views of the rest of the UK to be heard.

"I am not convinced that a shared currency would work from the Welsh perspective.

"I would be uncomfortable being part of a currency union where there are competing Governments trying to run it. If there is a disagreement, who has the final say? This is a recipe for instability - and these things matter, particularly in times of crisis."

The monetary union proposal will be at the heart of the Scottish Government's independence White Paper, the blueprint for the go-it-alone state, which will be published in Glasgow on Tuesday. Under the SNP's plans, an independent Scotland would seek to forge a currency union in the 18 months between a Yes vote and formally leaving the UK in 2016.

Last week the Scottish Government's head of strategy, Colin McKay, confirmed the plan could not be guaranteed and Chancellor George Osborne has already warned the UK would be unlikely to support it.

However, Scotland's First Minister has insisted a currency union will happen, arguing it would be in the interests of both countries.

Mr Jones questioned the wisdom of the proposal for an independent Scotland, saying the country "would be at the mercy of monetary policy determined in London".

He added: "So what use ­independence in those circumstances? If you use someone else's currency, then you are bound by their rules."

Mr Jones, a lawyer and fluent Welsh speaker, leads the minority Labour administration at Cardiff Bay.

He used the address to argue for a UK-wide constitutional shake-up in the event of a No vote in Scotland next year.

Calling for an end to "ad hoc ­tinkering" he said the UK needed a stable constitutional framework with the status and powers of devolved governments enshrined in law.

He said the UK Government's recent agreement handing the Welsh Assembly similar tax raising powers to Scotland showed further devolution would be possible if Scots voted No.

He said: "To my mind to be a Unionist in the 21st century is to be a devolutionist."

SNP MSP Linda Fabiani said: "The chairman of the No campaign, Alistair Darling, described a sterling area between an independent Scotland and the rest of the UK as 'logical' and 'desirable', which indeed it is.

"And Scotland's export strength, including North Sea oil, would be to the huge benefit of the sterling area, including Wales."

A spokesman for pro-Union group Better Together said: "If anyone wanted an example of just how detached from reality the nationalists are, then they need only look at Linda Fabiani's latest nonsense.

"On the day that the First Minister of Wales blew yet another hole in their deluded currency claims, the nationalists are trying to say that the currency union's biggest and most vocal critic is, somehow, actually in favour of it. Comments like these make them look utterly ridiculous."