Opposition Leader Stéphane Dion accused the Conservatives of misleading and lying to Canadians after they rolled out new advertising against the Liberals' carbon tax plan on Monday.

The Conservative Party began running multimedia ads at southern Ontario gas stations mocking Dion's plan, the details of which have yet to be released. In one of them, a cartoon depicting a grease spot says, "Stéphane Dion said he wasn't going to introduce a carbon tax, but now he is, so gas and everything else is going to cost you even more. Yet another flip-flop. Better not fall for this trick."

During question period Monday, Dion said "the attack ads are misleading and a lie," adding that instead of taking seriously his call for a national debate on carbon pricing to fight climate change, the Conservatives offered a cartoon, "a talking grease spot."

"When are the Conservatives going to stop insulting Canadians and offer a real plan to tackle climate change instead of cartoons and a campaign of lies," he asked.

Secretary of State Jason Kenney defended the ads, saying that the Liberals have flip-flopped and want to impose a carbon tax that would increase the price of gas and "the price of just about everything."

NDP MP Thomas Mulcair criticized both parties, saying the Liberals' plan isn't going to do anything to reduce greenhouse gas emissions and demanded to know when the Conservative government was going to protect consumers with gas prices reaching $1.50 a litre in some parts of the country.

David Anderson, parliamentary secretary to the minister of natural resources, said the government has moved on this already in significant ways by lowering the GST and income taxes.

Last month, Prime Minister Stephen Harper described Dion's plan as "foolish and unnecessary" when asked what role the government could play in cushioning the impact of high oil and gas prices on consumers.

Harper said that beyond providing some tax relief, the government can have little impact on lowering gas prices.

Dion said Monday the Tory government admitted in its own climate change plan that it will create an increase in energy prices, particularly for electricity and natural gas.

"Will they admit that the so-called plan will lead to higher energy costs for Canadians?" he asked.