Stephen Harper, Canada's prime minister, has vowed to block an opposition move to bring down his Conservative minority government.

"Tonight I pledge to you that Canada's government will use every legal means at our disposal to protect our democracy, to protect our economy and to protect Canada," Harper said in a nationally televised address on Wednesday.

The leaders of Canada's three opposition parties agreed this week to join forces with the aim of toppling the minority government, accusing it of failing to act over the nation's economic crisis.

The parties had said a no-confidence vote would be held on December 8 in a bid to wrest power from Harper.

However, Harper is widely expected to go to Michaelle Jean, the country's governor-general, on Thursday and ask her to suspend parliament until his government delivers a budget on January 27.

Row over economy

Stephane Dion, the leader of the opposition Liberal party, in a letter to Jean on Wednesday urged she to reject Harper's request, arguing that it would prolong a parliamentary crisis and worsen the country's economic difficulties.

Jean has the final say on constitutional matters as the representative of Queen Elizabeth, the British monarch who is also Canada's head of state.

The government's budget is expected to include an economic stimulus package that opposition parties have been demanding.

Shutting down parliament for up to two months would also give Harper some time to try to resolve the political crisis.

In his speech, Harper accused the Liberals of plotting with the New Democrats and separatist Bloc Quebecois, "whose avowed goal is to break up the country".

According to a new opinion poll, 64 per cent of Canadians do not back Dion to be prime minister in a coalition government, but 53 per cent are also against the Conservatives' current economic policy.

The crisis comes just seven weeks after Harper was re-elected with a stronger mandate but still a minority in the country's third election in four years.