Ontario's Liberal government will introduce legislation tomorrow to implement a provincewide ban on the cosmetic use of pesticides, keeping one of their key election promises from last year.

Premier Dalton McGuinty promised the pesticide ban during last fall's election campaign after intensive lobbying from environmental activists and health professionals.

McGuinty and Environment Minister John Gerretsen will visit a private home in Toronto tomorrow – Earth Day – to announce the ban on the cosmetic use of pesticides on lawns.

Gerretsen was reluctant to reveal any details today, but said members of the public who visited the ministry's website overwhelmingly supported the ban.

"We always said it was a priority when we came out with our platform last year, and it's had tremendous support around the province from what we've received as far as the environmental registry is concerned," Gerretsen said. "Ninety per cent of the people that responded to it responded in a favourable way."

The provincewide ban is aimed at replacing a patchwork of local pesticide bylaws, but Ontario farmers will be exempt. There's no word yet if the province also plans to exempt golf courses from the ban.

The Conservatives and New Democrats said today they would likely support the legislation, but they first want to make sure the ban will actually help the environment and isn't just a public relations move by the Liberal government.

"I think our inclination is to probably support it, but at the same time we want to hear from the folks who are experts in this area, and whether they think it's all politics or whether there is going to be some meaningful benefit to the environment," said Opposition Leader Bob Runciman.

"We've seen a lot of initiatives from this government that don't have a lot of substance but look good and tend to make headlines, and this is maybe another one."

NDP environmental critic Peter Tabuns said he wants a ban that includes real penalties for people who continue to use pesticides for cosmetic purposes.

"If they bring forward legislation that has teeth in it, that's useful, then obviously we're going to be inclined to support it," Tabuns said. "But we don't know what they're bringing forward. We don't know if it's going to be useful or just simply fluff."

The Ontario College of Family Physicians has said the long-term effects of exposure to pesticides can be devastating, especially to pregnant women and children, leading to learning disabilities, birth defects and miscarriages.

The Canadian Cancer Society, the David Suzuki Foundation, Environmental Defence and the Ontario Medical Association have all urged Ontario to follow Quebec's lead and pass the ban on pesticides.