Brand new Liberal leader Michael Ignatieff said Wednesday he would honour the days-old coalition with the NDP to topple the Conservatives.

"I am prepared to form a coalition government, and to lead that government and provide Canada with the security and stability it needs," Ignatieff said in Ottawa Wednesday afternoon.

"Canadians are worried about their jobs, their savings, and their future. They want stability, they want leadership and they want a government they can trust," said Ignatieff during his inaugural press conference as interim Liberal leader.

Earlier this month, Ignatieff appeared to be lukewarm on the idea of the coalition, which requires support from the Bloc Quebecois to bring down the Tories.

Ignatieff stressed that Prime Minister Stephen Harper's Conservatives will be defeated in Parliament early next year unless they table a budget which adequately addresses the financial malady gripping the global economy.

Ignatieff, who was crowned interim leader Wednesday afternoon by the party's national executive, added that Harper must take the first step and reach out to the Liberals to avoid losing power.

Still, Ignatieff hinted he would be open to working with the Tories.

"He has to seek and restore the trust that's been broken with other parties," Ignatieff said, choosing his words carefully. "We might oblige."

But Ignatieff told CTV's Mike Duffy Live that to work with the Conservatives in Parliament, the Liberals will require more than just a Tory-backed stimulus package.

"This isn't just about the budget, this is about a prime minister changing the tone in the House of Commons," said Ignatieff, adding that Harper must ditch his "my way or the highway" style of government.

"You can't run a minority Parliament like this: we are fed up with it, we won't have it anymore."

While NDP Leader Jack Layton seems intent on toppling the Tories in January no matter what, Ignatieff struck a more diplomatic tone Wednesday.

"Canadians can't trust us politicians if we say things like 'I'm going to vote against the budget even though I haven't seen it,'" Ignatieff said.

"It seems to me, that (approach) treats the Canadian people with disrespect."

Grit backroom pushes for Ignatieff

Ignatieff became leader after the party consulted with about 800 influential Liberals from across Canada, and follows a caucus meeting held earlier in the day in which MPs also endorsed the new leader.

In a media release, party president Doug Ferguson said Ignatieff will take over the party's top job at a "historic" moment.

"Our interim leader will be called upon to lead our caucus and our party through a volatile Parliament, and a possible federal election in the midst of the worst economic crisis in memory," Ferguson said Wednesday afternoon.

During the Grit caucus meeting in Ottawa Wednesday morning, Bob Rae, who withdrew from the Liberal leadership race Tuesday, nominated Ignatieff for the leadership position.

That nomination was then seconded by another former leadership contender, New Brunswick MP Dominic LeBlanc.

After the nomination, Ignatieff delivered a speech saying the Liberals would respect the coalition but that voting down the Jan. 27 budget was not absolute, CTV's Ottawa Bureau Chief Robert Fife reported Wednesday.

"He's leaving all options open for himself."

Fife also said senior Liberals have told him that they may not need a coalition to form a new government.

"If they do defeat the Conservative government ... Ignatieff will go to the Governor General and say 'We think we can form the government but we don't have to do it with a coalition,'" Fife said.

Fife noted that the NDP and Bloc would have to support the Liberals because they already have expressed opposition to the Conservative government.

Tories plan to strike

Meanwhile, the Tories were already planning their political response.

The strategy will focus on Ignatieff directly, and the Tory national machine has began asking for donations by labelling him a "parachute" leader, The Canadian Press reported Wednesday.

In a message to Conservatives, national campaign chairman Doug Finley slammed Ignatieff for bypassing the Liberal tradition of facing off against rivals during a democratic leadership convention, according to CP.

Conservative Heritage Minister James Moore said on CTV's Mike Duffy Live that his party is looking for Ignatieff to bring forward "reasonable proposals" as Liberal leader.

But Moore had strong words about the proposed coalition, which Ignatieff has not ruled out.

"It's a bunch of platitudes and rhetoric -- there are no specifics in there, no numbers," Moore said of the document the three opposition parties signed.

Ignatieff responded to those reports and called them unproductive and unwelcome at a time of parliamentary crisis.

He added that Harper and the Tories should back away from any aggressive political attacks.

"Look where it's got him, I think he should walk back," said Ignatieff.

In early January, the Liberal caucus will again come together for a three-day strategy meeting.

Then Ignatieff will travel across Canada to try and raise money to help fund the cash-strapped party.

Ignatieff will be named as permanent leader at the Liberal convention in Vancouver next May.

Fife said Ignatieff is a real "game-changer" and the Tories are worried about him.

"He's an international scholar, international well-known journalist, he's smart and he has around him hard-nosed political operatives who know how to play the game of politics," Fife said.