Shadow chancellor Ed Balls, who first proposed the idea at last month’s Labour conference, called on chancellor George Osborne to help “ensure a more informed debate” at the next election.
He believes the Office of Budget Responsibility (OBR) should verify the “costings of political parties’ manifesto commitments on spending and tax”.
“We would support any changes needed to the OBR’s charter and primary legislation and would seek to build cross-party consensus to achieve it,” Balls wrote in a letter to Osborne.
But Tory MP Andrew Tyrie, chair of the Treasury committee, said Labour had rejected a near-identical proposal three years ago.
“In 2010, the Treasury committee recommended that the OBR should have absolute discretion over the work it undertakes,” he said.
“I made clear in the Commons that this should include examining, at their request, the fiscal policies of opposition parties at election time. Both the government and the opposition rejected this approach at that time.”
The proposed legislation would amend the Budget Responsibility and National Audit Act.