The Conservative ads use footage from the Liberal leadership debate. (CBC)

The Conservatives unveiled three new television ads Sunday attacking Liberal leader Stéphane Dion, a day before members of Parliament return to the House of Commons.

The English-language ads, which will be followed by a second series of French ads, assert that Dion is a weak leader who would take the country back to the past.

They also criticizeDion's record as environment minister, charging that greenhouse gas emissions went up and air quality went down under his watch between 2004 and 2006.

In response to the ads, Dion told CBC News, "[Harper] wants to spend all this money to try to attack me in a very negative way, and it'll backfire."

"Canadians will not be impressed by that."

Dion also criticized Harper's environmental record, saying that several months ago the prime minister said that greenhouse gas emissions didn't exist.

Theads use footage from last fall's Liberal leadership debates, including clips of Michael Ignatieff, now Dion's deputy leader, and Ken Dryden admitting that the Liberals failed to meet the Kyoto targets for emission reductions.

One ad includes a clip of Dion plaintively responding to attacks on his environmental record, telling Ignatieff he doesn't know how hard it is to set priorities.

B.C. Conservative MP James Moore said, "We think that Stéphane Dion has been getting a little bit of a free ride. We're going to hold him accountable for the things he didn't do as environment minister."

The Conservatives, who have secured a prized spot for the ads during next weekend's Canadian broadcast of the Super Bowl, refused to say how much the party is spending on the election-style campaign.

With files from the Canadian Press