GORDON Brown must clarify whether Scottish Labour's plan for a federal UK would require a referendum before it could be introduced, the Scottish Conservatives have said.

The former prime minister, who is expected to campaign in the General Election today, has been a driving force in promoting the argument for a federal UK.

Scottish Labour leader Kezia Dugdale previously announced that she would join forces with Brown and others to look at how Labour can take forward plans for a People's Constitutional Convention that will examine how power is distributed across the nations and regions of the UK.

Adam Tomkins MSP, Scottish Conservative constitution spokesman, said: "To move to a federal UK would mark a historic and monumental constitutional change.

"As a leading proponent of the idea, Gordon Brown has to spell out how it would be achieved."

"Kezia Dugdale has raised the prospect of presenting it as an option in a second referendum on Scottish independence and, as we see Labour cosying up ever closer to the SNP, that is bound to set alarm bells ringing.

"Gordon Brown and Scottish Labour need to come clean about exactly what they are planning."