The coalition says that important environmental policies, like the implementation of the Ontario Greenbelt, are in jeopardy as parties prepare their platforms for an October 6 provincial election.
"There's a lack of clarity around the messaging coming from the various parties around what they feel is important," said Kristopher Stevens, a spokesman for the Ontario Sustainable Energy Association, one of the groups involved.
"If they're going take something away, what are they going to do to help us clean up the air and make sure things are better in Ontario?"
The Ontario Sustainable Energy Association and others have started a website, comeclean.ca, which invites voters to submit questions to politicians on environmental issues. The site will track responses from elected officials.
The campaign also includes a series of radio ads.
"Take the green belt away and you will get more cars. More cars and less nature," says one of the radio ads.
Another message in the ads addresses the issue of coal versus solar power.
"I'm worried about our jobs being taken away because some politicians don't like solar power. Do they like dirty coal? They should come clean."
The campaigners say the province has made huge strides on environmental issues in the past decade.
But with the election coming this fall, they say those gains are in danger.
"Ontarians are quite rightly concerned that some elected officials might take away some things that are quite important to them," said Adam Scott, a spokesman for Environmental Defence.
Scott said politicians and parties have made conflicting statements about environmental rules.