Senior administration officials have warned the Canadian government that a proposal to help Canadian clothing makers sell their products more cheaply in the United States violates the recently signed free trade agreement between the two nations and jeopardizes its ratification by Congress.

U.S. Trade Representative Clayton K. Yeutter expressed "strong displeasure" to Finance Minister Michael Wilson over the Canadian plan to allow its manufacturers to import fabric duty-free if they make it into clothing for export. Yeutter delivered the protest to Wilson Sunday at a meeting they attended in Switzerland, aides said yesterday.

"It darn sure creates a major ratification problem," said another senior administration official, who added that he has been hearing complaints about the plan from Capitol Hill.

"The future isn't all that good for the free trade agreement" if Canada goes ahead with the duty remission plan. "That's my opinion," said the chief U.S. negotiator on the pact, Peter Murphy.

He delivered the first official U.S. protest on the proposal last month, telling Canadian Ambassador Allan E. Gotlieb that the plan "violates the standstill provision" of the free trade agreement. This calls for both governments to refrain from taking new protectionist measures while the agreement is being ratified.

This type of duty-remission plan would be barred after June 30 under the free trade agreement, which was reached in principle Oct. 3 and signed Jan. 2 by President Reagan and Prime Minister Brian Mulroney. Duty-remission plans in place before June 30 can continue for another 10 years.

The issue surfaced last week when the American Textile Manufacturers Institute released a Nov. 16 letter from Canada's minister of regional industrial expansion, Robert R. de Cotret, telling the Canadian industry that the Mulroney government was rushing to implement a duty remissions plan before June 30.

"If the Canadian duty-free remissions scheme is put into effect, we will have no choice but to oppose the U.S.-Canada Free Trade Area Agreement in the strongest possible terms when it comes to Congress for approval," ATMI president Robert G. Laidlaw said in releasing the letter.

While many U.S. lawmakers and industries object to parts of the agreement, it appears now that these complaints are too narrowly focused to defeat the pact. But the ATMI is considered to have enough clout with Congress to form a strong nucleus for the opposition to coalesce around and could tip the balance against the pact. Canadian officials have assured the Reagan administration that the duty-remission plan has not won approval of the Mulroney government.

But the de Cotret letter to Oskar Rajsky, chairman of the Canadian Apparel Manufacturers Institute, makes it appear the government is racing to beat the June 30 deadline with a duty-remissions plan. "The provisions of the Canada-USA FTA {free trade agreement} have led the government to consider how it can develop an urgent and integrated response to the various apparel remissions proposals," de Cotret wrote.

"In view of this fact," the letter continued, "my colleague, the Honourable Michael Wilson, minister of finance, has decided to proceed with an important duty remissions program for the apparel industry prior to the June 30, 1988 deadline."

On Capitol Hill, meanwhile, Treasury Secretary James A. Baker III met with Senate Finance Committee Chairman Lloyd Bentsen (D-Tex.) to set a timetable for congressional consideration of the agreement.

Bentsen and House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) have insisted that a full consultation with the administration on the provisions of the agreement take place before formal consideration starts in June.