Canada's three opposition parties signed an agreement yesterday to form an unprecedented coalition government as they moved to oust the minority Conservative government in a coming confidence vote.

The accord between the Liberals, New Democratic Party and the Bloc Quebecois came after Liberal members agreed that outgoing leader Stephane Dion would stay on to become the interim prime minister of the Liberal-NDP coalition government, with support from the Bloc Quebecois.

A non-confidence vote over the Conservative government's economic policy is scheduled to be held in the parliament next Monday. If the vote happens, Stephen Harper's minority Conservative government will collapse. The oppositions will then ask the governor general to allow them to form a coalition government.

The current political storm erupted last week after Finance Minister Jim Flaherty unveiled his economic update, a blueprint that disappointed the oppositions by containing no stimulus package and outlining plans to slash public funding for political parties.

The oppositions immediately denounced the update, saying they have lost confidence in the government for having not taken effective measures to deal with the economy.

Under the opposition accord, the proposed coalition cabinet will be composed of 24 ministers and the prime minister. Six of these ministers will be appointed from within the NDP caucus.

The accord will expire on June 30, 2011, unless renewed. It says an economic stimulus package will be the new government's top priority. It also commits to "pursuing a North American cap-and-trade market" to limit carbon emissions.

Liberal leader Stephane Dion said he would advise Governor General Michaelle Jean later in the day in a letter that he has the confidence of the Commons to form the government should the Conservatives be defeated in a confidence vote.

But analysts say Prime Minister Stephen Harper may announce proroguing the parliament to give himself more time to fight off the oppositions. Or if the government falls, the governor general may choose to hold a snap election.