BELLEVILLE, Ont. - The Ontario Liberals aren't letting controversy over some of their green energy plans scare them away from their commitment to a cap-and-trade system.

But while Premier Dalton McGuinty stands firmly behind green technology, he said Wednesday he'd only put a cap-and-trade system in place under strict conditions.

"We're not going to get into a cap-and trade system unless we get the right kind of cap-and-trade ... one that's going to benefit Ontarians," McGuinty said during a campaign stop in Belleville, Ont.

"If it's not something that serves to benefit our economy, we're not going to do it."

Cap-and-trade is a system that seeks to control pollution by providing economic incentives for achieving reductions in polluting emissions.

It's different from the carbon tax that former federal Liberal Leader Stephane Dion pushed without success in the 2008 federal election -- one that critics called confusing, expensive and politically risky because many voters tend to see it as a money grab.

Cap-and-trade is designed to force businesses that produce greenhouse gas-causing emissions to find efficiencies, and puts limits on the amount companies are able to pollute. Those that are over the limit have to buy credits from those who are under.

"Cap-and-trade is a system that works to the advantage of businesses and jurisdictions that reduce their emissions. Guess who's done more to reduce their emissions in all of North America? We, the people of Ontario," McGuinty said.

"We've got a big advantage and we have to find a way to turn that into a financial advantage for Ontarians."

McGuinty dismissed questions about why his plan for a cap-and-trade system wasn't in his party's election platform, after the Progressive Conservatives accused the Liberals of playing with potential tax increases.

The Tories pounced all over a gaffe by Liberal candidate Dave Levac, who mistakenly said the Liberals were considering a carbon tax. He later issued a statement correcting himself and explaining he "confused cap-and-trade with a carbon tax."

The PCs also suggested in an ad Wednesday that McGuinty supported Dion's carbon tax proposal -- an endorsement the Liberals say never happened. McGuinty himself has said in the past he does not support a carbon tax.

"Everyone knows that we're a part of, for example, of the Western Climate Initiative," said McGuinty, once again ruling out a carbon tax.

"People know that we support a cap-and-trade system."

Such a system is still years away for Ontario since the province doesn't have any partners yet and would have to negotiate the deals.

But it's also be a possibility under a New Democrat government, said Leader Andrea Horwath.

"We've said very clearly that carbon tax is not something that we favour," she said.

"We are certainly committed to working towards the Western Climate Initiative so that we have a number of different jurisdictions that are participating in a cap-and-trade program. It's something we're going to strive towards."

Progressive Conservative Leader Tim Hudak said he would like to see a plan to deal with greenhouse gas emissions "not simply on a provincial basis, not even on a national basis, but on a continent-wide basis."

"What I won't do is pass on a big tax increase (to Ontarians) or take up initiatives that are going to cost us even more jobs in Ontario," he said.

British Columbia is the first jurisdiction in North America to introduce a consumer-based carbon tax.

Ontario's Green party, which holds no seats in the legislature but is running candidates in all 107 ridings, has promised to bring in a carbon tax based on the B.C. model and involving a $10 tax per tonne of carbon emitted.