OTTAWA - Interim Liberal leader Bob Rae is asking the governor general to overrule the House of Commons and Senate by withholding his signature from the Canadian Wheat Board Act.

"The government will almost certainly seek royal assent for this legislation in the coming days," Rae wrote in an open letter to Gov. Gen. David Johnston. "As leader of the Liberal Party, I would ask most respectfully that full consideration be given to awaiting final disposition of this matter by the courts before the legislation receives royal assent."

The Senate is likely to give third reading on Thursday to Bill C-18 to make the Canadian Wheat Board voluntary for Western farmers.

Rae admits his request is "rather unusual" but insists it wouldn't be right to see the bill signed into law after the Federal Court ruled Agriculture Minister Gerry Ritz should have held a farmer plebiscite on the issue before bringing the bill to the House of Commons.

The governor general's office did not respond to requests for comment, but a September report from the University of Saskatchewan's student newspaper, The Sheaf,indicated Johnston was reluctant to step into the wheat board controversy.

Johnston told students it wouldn't be appropriate for the governor general to effectively veto a bill passed by Parliament.

Rae's call for Johnston to use a power that no modern governor general has used before comes on the 80th anniversary of the Statute of Westminster, which ended Britain's power to pass laws for this country.