Last month at the Labour Party conference, Ed Balls announced Labour's intention to submit its manifesto for scrutiny by the Office for Budget Responsibility to confirm it contained no uncosted spending commitments, and called on others to follow suit.
The Tories dismissed the proposal as a "stunt", insisting the OBR's charter did not allow it to undertake such work.
Now, the Shadow Chancellor has drafted a parlia-mentary amendment to introduce the change, which could be applied to the UK Government's forthcoming Finance Bill, drawn up after every Budget.
In a letter to the Chancellor, Mr Balls says: "I hope you will support this important reform, which I believe will enhance the role of the OBR while maintaining its impartiality and independence and ensure a more informed debate in Britain at the next election."
Mr Balls has also written to Andrew Tyrie, chairman of the House of Commons Treasury Committee, and Robert Chote, who chairs the OBR, to seek support.
By last night, there was no response from the Chancellor, who is in China, but it would be a surprise if he supported the move.