MONTREAL -- The number of Canadian condominiums owned by foreign residents grew over the past year in Vancouver, Toronto and Winnipeg, says the Canada Mortgage and Housing Corp.

CMHC released a survey Thursday that sheds some light on what has been a politically charged issue, particularly in British Columbia.

It says foreign buyers owned 3.5 per cent of condos in Vancouver in 2015, up from 2.3 per cent last year. That's the highest rate of all 16 metropolitan areas tracked in the agency's research.

In Toronto, the rate of foreign ownership rose to 3.3 per cent this year, up from 2.4 per cent the year before. The rate of foreign ownership in Winnipeg's condo market rose to 2.7 per cent, a jump from 0.1 per cent last year.

Concerns have arisen recently that wealthy foreign buyers are driving up the cost of homes in Vancouver, making them unaffordable for local residents. Critics have suggested that the market could crash if those buyers decided to cash out and sell.

CMHC CEO Evan Siddall said there's not enough data to predict what, if any, impact foreign investors are having on housing prices.

"The potential impact is if all that money leaves at the same time, which is probably not likely because they would all have to be subject to the same personal factors in the same country," he said after speaking to the Montreal Board of Trade.

The federal housing agency says it is exploring ways to broaden the scope of its research to include other types of housing, such as single family homes.

CMHC says more information is also needed about what is motivating foreign buyers. For example, some may be purchasing properties to house their families, while others may be seeking revenue, either by renting the property out or by selling it when its value increases.

CMHC began to survey foreign ownership in condos last year. It is now talking to Statistics Canada and local real estate organizations to broaden the survey to include house ownership.

Montreal was one of the few cities where the rate of foreign ownership of condos fell, decreasing to 1.3 per cent from 1.5 per cent.

For the purposes of the survey, the CMHC defined a foreign resident as a person whose primary residence is outside of Canada.

During his speech, Siddall flagged general housing affordability as a "key concern." The average Canadian spends a little more than 20 per cent of their total income on housing, he said, but it is nearly double that for the bottom 20 per cent of income earners.

He also touched on housing conditions for aboriginals on reserves, noting that nearly 40 per cent of natives live in dwellings in need of major repair.

"We must do better," he said. "And since Canada's aboriginal population is growing rapidly, we are falling further behind."