International Trade Minister Stockwell Day says politicians should not jump to build protectionist walls in response to voters angry about U.S. policies that shut out Canadian companies.

Day said municipal politicians who advocate retaliating against the U.S. for not using Canadian companies under a "Buy American" plan are only making matters worse.

Day was talking about a motion proposed by the Federation of Canadian Municipalities that suggests U.S. firms be shut out from contracts in Canada if they won't use Canadian companies in America.

The minister on Wednesday told the International Economic Forum of the Americas in Montreal that building new walls between trade partners is dangerous, especially during economic downturns.

Day said it's only natural that politicians in democracies like the United States would respond to their constituents' demands to protect local jobs.

But he said history demonstrates such actions are misguided, since they only hamper prosperity.