The New Democrats wasted no time challenging the minority Liberals to show they can work with the opposition parties by bringing in a bill to take the provincial portion of the HST off home heating.

"The Conservatives are very supportive of our initiative," NDP Leader Andrea Horwath said Wednesday as business officially resumed at the legislature following Tuesday's throne speech

"What's going to unfold will be an interesting conversation about who's prepared to actually start compromising a little bit and accepting the ideas that people are bringing to the table."

Taking the HST off essentials like home heating was a key election promise by both the NDP and the Progressive Conservatives, who have said they would support such an effort.

With a combined vote count of 54, the opposition parties feel confident they can get the bill through, although the minority Liberals have the power to prevent it from getting to third and final reading, and have vowed to do so.

"That proposal would cost the Treasury $350 million annually, to say nothing of the fact that first we'd have to obtain the consent of the federal government to that change in the HST application," Premier Dalton McGuinty said during a question-and- answer session at the Ontario Economic Summit on Wednesday.

"We have a different idea — we're proposing a healthy home renovation tax credit."

That's the legislation the Liberals introduced on the first day back, which is also based on an election promise of a $1,500 home renovation tax credit for seniors. It would cost $125 million annually and enable seniors to make their homes more user friendly, McGuinty said.

Progressive Conservative Leader Tim Hudak said he hoped the Liberals would reconsider their plan to block the HST bill.

"In a minority government I would hope that Dalton McGuinty would get the message," said Hudak.

"Why doesn't he let his members just vote according to what they think their constituents think? Clearly this would be a popular initiative among families across our province."

Horwath agreed, arguing that if the Liberals let the bill go through to committee, it would be a signal to voters that they are willing to work with the opposition.

"I guess that's the challenge to the government," she said.

"They said in the throne speech that they're prepared to work together, they're prepared to look at other ideas, tomorrow will be the actual full test of that with the actual debate at second reading."

New Democrat Michael Mantha, who represents the riding of Algoma Manitoulin, introduced the bill Wednesday. It will be up for debate and a second reading vote Thursday.

Horwath did not approach Hudak to co-sponsor the bill, even though it was something both parties had included in their platform, but he still pledged his support early on.

The Tories campaigned on taking the provincial portion of the HST off heat and electricity bills, as well as removing the debt retirement charge from hydro.

The bill comes on the same day as Finance Minister Dwight Duncan delivered his economic update.