London mayor Ken Livingstone has said Scotland is subsidising the rest of the UK through its oil revenues.

Red Ken's view that the buoyant London economy and Scotland are together bankrolling the English regions and Northern Ireland will come as an unwelcome intrusion into the Holyrood debate for Labour.

Mr Livingstone said: "Having read all the stuff the SNP is putting out, it's most probably true that Scotland subsidises the rest of Britain if you take into account a classic international law interpretation of who the oil belongs to.

"It's northern England that is the major beneficiary of our subsidy, and Northern Ireland as well," he said in an interview with Prospect Magazine.

Stewart Hosie, SNP Treasury spokesman, said: "It's embarrassing and damaging to Labour's negative campaign in Scotland for the Labour Mayor of London to agree with the SNP that Scotland subsidises the rest of the UK.

"Mayor Ken is right and the Labour leadership entirely wrong."

Labour's Andy Kerr said: "There is a choice between building Scotland with Labour and breaking up Britain with the SNP. Sustained attack from Labour has led to support for independence almost halving in less than a month."