TORONTO, DEC. 15 -- A Canadian parliamentary committee today urged Prime Minister Brian Mulroney to scrap the tentative trade agreement with the United States unless Canada is formally exempted from the omnibus trade and textile bills now before Congress.

The recommendation by a House of Commons committee that is dominated by members of Mulroney's Progressive Conservative Party carries no legal force. But it appeared likely to cause trouble for Mulroney as he tries to win public support for the pact, which would remove all tariff barriers between the two countries during the next decade.

{In Washington, administration officials and lawmakers agreed that the proposal, if approved, would kill any chance of the United States going ahead with the agreement.}

Mulroney has attempted to sell Canadians on the trade pact by arguing that it offers Canada security of access to the huge U.S. market at a time of intense protectionist pressures in the U.S. Congress. But the prime minister has not made clear to Canadians -- nor, apparently to members of his own party -- that his representatives could not get explicit assurances from U.S. negotiators that Canada would be "shielded" from any future U.S. trade laws.

The controversy arose as the House of Commons began debate on a resolution of support for the trade agreement. Mulroney and President Reagan are to sign the accord on Jan. 2, but enabling legislation is not expected to be introduced until early next year. If approved by Congress and Parliament, the deal is to take effect on Jan. 1, 1989.

Leaders of the opposition Liberal and New Democratic parties have strongly opposed the agreement, arguing that it will cost Canadians jobs and lead to the erosion of national sovereignty. Most of their comments have been general and emotional, with neither of the opposition parties able to latch on to any specific flaw in the pact to rally public support for their views. The concern about the textile and omnibus trade bills could provide them with an opening.

Bill Winegard, chairman of the special Commons trade committee, said the question of whether Canada would be exempted from the U.S. legislation came up frequently during recent public hearings across Canada.

"The committee felt we should make our position quite clear to the government," Winegard said. "I would feel very upset {if there were no guarantees}. I have no doubt in the world that this will be resolved." The seven Conservative Party members and the four opposition members of the committee agreed unanimously that such assurances were essential.