OTTAWA—Imposing curbs on foreign investment in Canadian real estate could have unintended consequences for the broader economy, Canadian Prime Minister Justin Trudeau warned in a year-end interview with Canada’s Global Television Network, 

Mr. Trudeau said there is a lack of “concrete data” about the impact of foreign buying on Canadian real estate, so moving ahead without proper information is risky.

Mr. Trudeau’s comments emerge as a debate heats up over the impact overseas buyers may be having on housing affordability in the two of the country’s biggest housing markets—Toronto and Vancouver, British Columbia.

“You know you have to be cautious about decisions like that that are based on a single factor because at the same time [it] would potentially devalue the equity that a lot of people have in their homes right now,” Mr. Trudeau said, according to a transcript of the interview distributed by Global TV.

“We have to be very, very cautious about restricting foreign investment in our country at a time where we know we need foreign investment in businesses, in resource development.”

Economists indicate strong sales and price growth in Toronto and Vancouver are supported by job creation in the two metropolitan areas, and an increasing number of people migrating to those urban centers as resource-rich parts of the country suffer under the weight of low commodity prices, as opposed to foreign investment.

Meantime, Evan Siddall, the president of Canada Mortgage and Housing Corp., a government-owned mortgage insurer and housing agency, said in a recent speech that foreign investment could be contributing to the overvaluation of housing prices in the two markets. But, he said, the country lacks “accurate and reliable data” to determine the role foreign investment has on housing prices in the country.

CMHC data indicate foreign ownership of condominiums in Toronto and Vancouver edged up over the past 12 months, to 3.3% and 3.5%, respectively, from the low- to mid-2% range. The agency didn’t have data covering single-detached homes.

The role foreign investment might be playing in driving up housing prices and sales in Toronto and Vancouver has sparked calls for lawmakers to act to keep housing prices in check. Former prime minister Stephen Harper pledged during the 2015 election campaign that his Conservative Party would act to tackle overseas buying of real estate. Mr. Harper lost a bid to win a fourth-straight mandate.

And in a move this month targeting the Toronto and Vancouver markets, the Liberal government moved to cool down activity in housing by requiring first-time buyers to make larger down payments on pricier homes.

Other nations are struggling with foreign investment in real estate too. In Australia, the government has strengthened rules amid concerns Chinese buyers are driving up housing prices and making properties unaffordable for locals. Overseas buyers are prohibited from purchasing houses in the resale market, although investment in new housing is allowed. Authorities in Australia estimate half of China’s total investment in the country is in real estate