Liberal Leader Michael Ignatieff speaks Tuesday during the Liberal caucus summer retreat in Sudbury, Ont. (Sean Kilpatrick/Canadian Press)

The Liberals say they will try to trigger the defeat of Stephen Harper's minority Conservative government at the earliest possible date this fall, delivering a message to the prime minister: "Your time is up."

In a campaign-style address to supporters in Sudbury, Ont., where his caucus is meeting, Liberal Leader Michael Ignatieff said Tuesday that Harper has failed to meet the four conditions the Liberals set out for him in June to remain in power.

"You’ve failed to protect the most vulnerable, you’ve failed to create jobs, you’ve failed to defend our health care, you’ve failed to restore our public finances," Ignatieff said.

"We cannot support this government any further. After four years of drift, four years of denial, four years of division, four years of discord, Mr. Harper, your time is up."

A Liberal government, Ignatieff pledged, would return "competence and compassion" to the federal government to replace an "incompetent" Harper government that "doesn't care."

"The secret weapon on our side is Stephen Harper's record," he said. "We can do better."

Vote could come Oct. 1, or sooner

Ignatieff also hit out at Harper for not seeing the recession coming and predicting during the last election that the government wouldn't run a deficit, while also failing to stand up for Canada and Canadians abroad.

"You can't count on a government that can't count," he said.

Ignatieff pledged a Liberal government would deliver on its "vision for rebuilding the Canadian economy," including expanding trade with huge, emerging markets in China and India.

The Conservatives, he charged, have sat back and done nothing all summer as Canada's health-care system is dragged through the mud in the United States.

"The Liberals are fiercely proud of our health-care system and, unlike the Conservatives, we are not afraid to defend it," he said.

Parliament resumes Sept. 14, and the Liberals will have their first opportunity to present a no-confidence motion on Oct. 1. Speaking after Ignatieff, Liberal MP Bob Rae said the party will present the motion "at the first available opportunity."

There is a chance a vote could come even sooner. The Conservatives could introduce a ways-and-means motion to implement some aspects of last January's budget, including the popular home renovation tax credit, as soon as Parliament resumes Sept. 14.

With Ignatieff's pledge, it now falls to the Conservatives to reach out to the two other opposition parties to prevent the government from falling.

NDP may offer olive branch to Tories

The NDP, which has voted against the government at every opportunity thus far, is now suggesting it may prop up Harper if he's willing to work with them. New Democrat MP Thomas Mulcair said the last thing Canadians want is another election.

"If Mr. Harper goes about being provocative as he has been in the past, going after key things that Canadians hold dearly like women's rights and the environment, then we'll throw him out of office because he'll have provoked it," Mulcair said.

"If, on the other hand, Stephen Harper comes into Parliament with a willingness to work in the public interest, then we're going to take it on a case-by-case basis. Our caucus will decide."

Mulcair said the Conservatives would have to offer pension protection, enhance employment insurance, protect against exorbitant credit card fees and halt the foreign takeover of Nortel to get NDP support.

"If Mr. Harper likes to pick up some of our themes, then perhaps Canadians could be spared their fourth general election in five years."

The Bloc Québécois, which has also voted against Harper's Tories in the past, has yet to comment on the latest Liberal sabre-rattling.

Harper says Canadians don't want an election

Speaking in Calgary, Harper said he hadn't met a single Canadian over the summer who wanted another election less than a year since the last vote.

"I think Canadians have been pretty clear — they want Parliament to focus on the economy," the prime minister told reporters as Ignatieff was still delivering his speech.

"It's certainly our view and I think the view of the vast majority of Canadians that going through more political games, more political instability, does not serve the country's interests right now. So we are planning to address the economy and that will be our focus."

Transport and Infrastructure Minister John Baird also criticized Ignatieff for wanting to plunge Canada into its fourth election in five years.

"Mr. Ignatieff is just asking for an election for reasons of political opportunism," Baird told reporters. "That's his only motivation. He's thinking of his own interests and not the interests of Canadians and that certainly is not good for Canada."

On Monday, Baird said Canada's economy is too fragile for a snap election and opposition parties would be "irresponsible" to trigger one just as the economy shows signs of rebounding.

Party ready for election: Ignatieff

Ignatieff insisted his party is ready for a fall election because it has broadened its membership, brought in new ideas and revamped its fundraising campaign.

"We are more united than we have been for a generation," he said.

Last November's federal election handed the Liberals, then led by Stéphane Dion, the worst result in terms of popular vote in more than 100 years.

The tumultuous months following the vote saw the Conservatives infuriate opposition parties with a controversial economic update that prompted a failed attempt by Dion and the Liberals to form a coalition with the NDP, with the support of the Bloc, to oust the Tories from power.

In December, Harper persuaded Gov. Gen. Michaëlle Jean to prorogue Parliament to stave off a no-confidence vote and the demise of his minority government.

Dion resigned as Liberal leader shortly afterward, paving the way for Ignatieff to be named his successor and agree to support the Harper government's January budget, which outlined five years of deficits and billions of dollars for stimulus spending to boost the slumping economy.