Ontario (Reuters) – Canada's main opposition Liberal Party on Tuesday vowed to bring down the minority Conservative government, leaving the fate of Prime Minister Stephen Harper in the hands of other parties.

In a risky announcement that offers no guarantee of electoral success, Liberal leader Michael Ignatieff said Harper had failed to help Canadians deal with economic crisis.

The Liberal Party cannot support this government any further. We will hold Stephen Harper to account. We will oppose his government in Parliament, he told cheering members of the Liberal Parliamentary caucus in Sudbury, Ontario.

The Liberals now want to bring in a non-confidence motion in the government once Parliament resumes later this month.

Provided all three opposition parties vote against the government, that would mean an election in late October or early November, a year after the last federal election.

The left-leaning opposition New Democrats, who have repeatedly said they will oppose Harper, took a cautious line.

We're going to wait and see exactly what the Liberals are going to table. We're not going to jump in and speculate as to how we'll go, New Democrats national director Brad Lavigne told the Canadian Broadcasting Corp.

The leader of the separatist Bloc Quebecois -- no friend of Harper -- will react to Ignatieff's announcement at 4 p.m. EDT (2000 GMT) on Wednesday.

Polls show the Liberals and Conservatives deadlocked at around 32 percent support, well below the 40 percent needed to guarantee a majority in the 308-seat House of Commons.

I guess I want to know -- are they crazy? National Post columnist Don Martin told the Canadian Broadcasting Corp.

Harper won his first minority government in January 2006 and increased his grip on power in October. The Liberals have kept him in power by backing key legislation, including the budget, putting them in the awkward spot of attacking the government with words but not with votes.

THREATS

The party has saber-rattled about an election before, only to back down, most recently in June when the Conservatives agreed to set up a bilateral panel on jobless benefits.

But Ignatieff's uncompromising language on Tuesday indicates he no longer sees any room for compromise.

After four years of drift, four years of denial, four years of division and discord, Mr. Harper, your time is up, he said to a standing ovation.

Harper says Canadians do not want an election now, and a vote would imperil a C$46.2 billion ($42 billion) two-year stimulus package unveiled in the January budget.

I think it's pretty clear Canadians want Parliament to focus on the economy, he said in Calgary.

Canada's dollar dipped briefly, and then recovered.

The political developments just add a little more uncertainty and that's a negative for the Canadian dollar, said RBC Capital Markets technical strategist George Davis.

Ignatieff took over as Liberal leader last December after the party did poorly in the October election. Since then he has revitalized the party and helped it raise the money it will need to fight an election.

Yet the former Harvard academic and professional journalist could be vulnerable to attacks from Conservatives, who say the decades he spent outside Canada mean he had little idea what Canadians need or want from their government.

(Additional reporting by Scott Haggett, Louise Egan, Frank Pingue, Jennifer Kwan and Ka Yan Ng)

(Writing by David Ljunggren)

Canada Down