ALISTAIR Darling has described the SNP's plan to forge a currency union with the rest of the UK, if voters back independence, as a "Heath Robinson affair".

He likened the proposed monetary union to one of cartoonist William Heath Robinson's complicated contraptions following a speech to students in Edinburgh yesterday.

The former Chancellor and head of the pro-UK Better Together campaign said the currency plan was "increasingly dead in the water" after warned a future UK Government would not agree to such a deal. He said: "Does he not accept that a currency union needs both Scotland and the rest of the UK to agree to enter into it?

"Should he not accept a currency union means both sides have to agree each other's budgets?"

Commenting later, he added: "All European Union members have to submit their budgets for approval to the European Commission. I think it's profoundly anti-democratic. It means if Scotland and the rest of the UK entered into a union, you'd have to agree each other's tax and spending.

"But if Alex Salmond insists there is a glimmer of hope here, given he can't deliver it as it takes two to work, he has got to have a fallback position.

"What he is proposing is a real Heath Robinson affair."

Mr Darling also said he hoped to share a platform with Gordon Brown during the independence campaign.

His comments were dismissed as "panicky" by SNP Westminster leader Angus Robertson, who said a poll showed support across the UK for use of the pound in an independent Scotland.