Dec. 1 (Bloomberg) -- Canadian opposition party leaders agreed to try and oust Prime Minister Prime Minister Stephen Harper’s minority Conservative government, signing an accord to work as an alliance until June 30, 2011.

Liberal Party Leader Stephane Dion would lead the government if Harper is defeated, he and other party chiefs said today in Ottawa. The Liberals would have 18 cabinet posts including finance, and the New Democratic Party would get six cabinet jobs.

“We are seeing a sad spectacle from Harper’s government,” Dion said at a press conference in Ottawa after a signing ceremony, flanked by Bloc Quebecois Leader Gilles Duceppe and New Democratic Leader Jack Layton. “We are ready to form a new government that will address the best interests of the people.”

Canada has never been led by a group of opposition parties since it was formed in 1867. The country’s closest thing to a coalition government was during World War I, when Conservative Prime Minister Robert Borden recruited opposition Liberals to run under a joint “Unionist Party” banner in a 1917 election.

Harper backtracked over the weekend from a Nov. 27 plan to scrap state funding of political parties and curb public sector strikes, in a bid to prevent the collapse of his government which was re-elected less than seven weeks ago. Harper’s Conservative Party holds fewer than half the seats in Canada’s Parliament and needs opposition support to stay in power.

‘Lost Confidence’

Finance Minister Jim Flaherty said yesterday that he would introduce a budget on Jan. 27, about a month earlier than usual. Harper, 49, also pledged to expedite an economic stimulus package, after opposition parties criticized him for not releasing one last week with Flaherty’s fiscal update.

“The government has lost confidence, lost the confidence of the people of Canada and the members of the House of Commons,” Layton said. “It has failed to act and it falls on us to act” to boost the economy, Layton said, adding Harper’s government “is going to be defeated at the earliest possible opportunity.”

Duceppe of the Bloc Quebecois, which would not be part of the governing coalition while supporting it until June 30, 2010 -- a year before the Liberal-NDP pact expires -- said the coalition would offer a bigger and faster spending package including support for manufacturing and forestry workers. Harper’s plan to cut corporate income taxes won’t be repealed, Dion said, something that the New Democrats had sought in the campaign ahead of Oct. 14 elections.

The coalition proposal requires the backing of the country’s ceremonial head of state, Governor General Michaelle Jean. She may also refuse their request, a decision that would trigger elections, the country’s fourth since 2004. Dion said he would ask Jean to invite him to form a government, without specifying when he will do that.

To contact the reporter on this story: Theophilos Argitis in Ottawa at targitis@bloomberg.net; Greg Quinn in Ottawa at gquinn1@bloomberg.net.

Last Updated: December 1, 2008 17:37 EST