The government of Quebec has strongly condemned Ontario's decision to retaliate against Quebec's trade barriers against out-of-province firms and construction workers.

Frances Lankin, Ontario's trade minister, announced Monday that Ontario will impose identical barriers.This means thousands of construction workers from Quebec could lose their jobs in Ontario. It follows a similar move several months ago by New Brunswick against Quebec's perceived protectionist regulations.

"I very strongly condemn the political posture of the Ontario government," said Gerald Tremblay, Quebec's industry minister.

Ms. Lankin added that there has been little or no progress in the issue despite negotiations over the summer. The Ontario government simply is seeking ''to level the playing field," she said.

Ontario will exclude Quebec-based contractors and construction materials

from future provincial government projects.

Among other actions, Ontario's Transportation Department will discourage the

purchase by Ontario municipalities of buses made in Quebec. This is a potential loss of US$8 million of annual business for Quebec bus manufacturers.

Last summer, amid rising tensions over the trade barrier issue, construction workers from Ontario blocked traffic on several bridges between Ottawa, the federal capital, and Hull, Quebec.

Because of its proximity to Quebec and the concentration of federal government offices in both Ottawa and Hull, the Ottawa region has been a flash-point in the conflict.

Canada's business community has been putting mounting pressure on the provincial governments to eliminate some 500 internal trade barriers that cost the Canadian economy an estimated US$5 billion a year.

Federal and provincial trade ministers have pledged to negotiate a comprehensive agreement by June 1994 on elimination of barriers inhibiting the free movement of goods and labor.