TORONTO -- Ottawa's move to tighten Canada's mortgage rules a year ago helped cool down the country's real estate market by forcing some first-time home buyers to delay their purchases, economists say.

A Bank of Montreal (TSX:BMO) study suggests roughly one in five potential first-time homebuyers have postponed their purchase since Finance Minister Jim Flaherty introduced his new lending rules a year ago Tuesday.

The rule changes included a reduction to the maximum amortization period to 25 years from 30 for insured mortgages.

It was the fourth time Flaherty tightened mortgage lending rules in as many years, incrementally dropping the longest amortization period from 40 years.

"It did take a bit of steam out of the market because it essentially forced quite a number of potential buyers, especially first-time buyers, to wait a while longer," BMO's chief economist Doug Porter said in an interview.

About 19 per cent of those polled by BMO said they decided to wait longer to buy their first home, while 66 per cent said the changes have not affected their timeline.

Meanwhile, 14 per cent said they planned to buy sooner.

A recent report by the Bank of Nova Scotia (TSX:BNS) estimated the mortgage rule changes may have pushed 10 per cent of potential buyers out of the market.

Both Porter and Scotiabank economist Adrienne Warren said the changes helped the country's overheated real estate market achieve its desired soft landing.

"I think it was almost the perfect soft landing for policy makers," said Porter.

"It cooled, but it didn't undergo a so-called hard landing. Sales did drop pretty heavily the first couple months, but then they stabilized and they've started to creep back up again."

Housing sales in the Greater Toronto Area were down by less than one per cent in June from a year ago while the average selling price climbed 4.7 per cent, according to recent figures from the Toronto Real Estate Board.

Meanwhile, sales in Vancouver were up about 12 per cent in June compared to the previous year.

Going forward, rising mortgage rates could block more prospective buyers out of the market, Warren said.

Mortgage rates have been at all-time lows since the economic downturn, but fixed rates have slowly started to rise in the past two months.

"The recent upward drift in mortgage rates could dampen housing demand in the second half of the year, especially in high-priced markets such as Toronto and Vancouver where affordability is more strained," Warren said in a statement.

The Bank of Montreal online survey polled 2,000 Canadians between Feb. 25 and March 5.

The polling industry's professional body, the Marketing Research and Intelligence Association, says online surveys cannot be assigned a margin of error because they do not randomly sample the population.