Four out of every 10 renting households in Canada spent almost a third of their income on rent, above the level that experts say is sustainable, affordable housing advocates said Thursday

Six affordable housing groups across the country Thursday unveiled the Rental Housing Index, an in-depth look at the finances of Canadian renters.

Based on data culled from Statistics Canada from 2011, the interactive, map-based index looks at the state of affairs in Canada's rental market. Despite constant headlines that seem to suggest home ownership is a Canadian obsession, more than four million households in Canada rent — that's about 30 per cent of all the households in Canada.

While homeowners in many markets are keenly aware of rising prices in recent years, the numbers Thursday suggest renters aren't immune to the increasing cost of housing.

Widespread problem

The problem is especially acute in some of Canada's biggest cities. In Toronto, the group says there are 105,215 rental households that spend more than half of their total income on rent. That's more than one out of every five renters in the city.

The ratio is based on gross income, which means the amount of money being spent on housing costs is actually even higher when one considers after-tax income.

In Vancouver, 136,025 households spend almost a third of their income on rent, and almost a quarter of the city's renters spend half their money on rent.

Montreal may be the most rental-heavy city in the country, due to rents that were for a long time comparatively low for a city of its size. But those days are long gone, the data suggests. Close to 60 per cent of the city's residents are renters, but more than one out of every five — or 108,875 in total — are spending half of their income on rent.

Nationally, 40 per cent of renters spend almost a third of their income on rent, and almost one in five spent half their money on it. Affordable housing experts say a ratio that high puts them at high risk of becoming homeless, which costs the broader system a lot to address down the line for things like health care and other social services, in addition to a long-term erosion of the tax base.

Officials on hand Thursday said it will take time and money to fix the problem, but stress that action is cheaper than inaction.

"All the symptoms that come up from housing affordability we have an unlimited amount of money for," said Tony Roy, chief executive officer of the BC Non-Profit Housing Association. "But all of those things are far more expensive than this core issue of rental housing affordability."

Roy said the federal government has paid to build roughly 650,000 social housing spaces over the years, many of which are desperately in need of upgrading and repairs. Most of those units were built prior to 1993.

"This isn't about more money being spent, it's about using our money in a more wise way," Roy said, noting that Ottawa spent $1.7 billion on social housing this year.

The issue has come up on the campaign trail, with the Liberals unveiling a plan that they say addresses the issue. The plan announced this week would provide $125 million per year in tax incentives for developers and landlords to build and renovate rental units, and would make investment in affordable housing and residences for seniors a priority.

Last month, NDP Leader Tom Mulcair said his party has a plan to create 10,000 social housing units "very rapidly" if his party forms the government.

A request for comment from the Conservative campaign on what its affordable housing policy is was not immediately returned.