Opposition parties have united behind a bid to change rules stopping them altering the Executive's £30billion budget.

Currently, only ministers can make changes to the annual budget when it comes before Parliament.

But public finance expert Professor Arthur Midwinter, a former adviser to Holyrood's Finance Committee, has claimed that committees should be allowed to make budget amendments under a minority government.

A spokeswoman for the Labour Party said today it was behind the move. "It's a different political climate and that's something we would support," she said.

Tavish Scott, the Lib-Dem finance spokesman, wants the measure brought before the new procedures committee at Holyrood.

He said: "With a minority government, the onus on the parliament now is to take responsibility."

Conservative finance spokesman Derek Brownlee added: "This is not something we should close our minds to."

An Executive spokes-man said that the new SNP government "sees no case for changing the arrangements".