Canada's Prime Minister, Paul Martin, faces a no-confidence motion in parliament which his minority Liberal government is widely tipped to lose.
Paul Martin's government is accused of losing its moral authority
It is expected that parliament would then be dissolved and an election called in January.
Three opposition parties are bringing the motion after Mr Martin rejected an ultimatum demanding a poll in February.
They claim his party no longer has the moral authority to lead in the wake of a corruption scandal.
The government has been dogged by allegations of irregularities over contracts awarded by a previous Liberal administration between 1997-2001.
Mr Martin is not implicated in the scandal, but the opposition says his government is tainted and should be forced out of office.
For their part, the Liberals have accused the Conservative Party of "false smears" and of trying to reverse decades of progress in Canada.
MPs are expected to vote at 1845 local time (2345 GMT).
Mr Martin's party holds 133 of the 308 seats in the House of Commons, while the three parties bringing the motion have a majority.
Conservative leader Stephen Harper said his party would join forces with fellow opposition parties the New Democrats and Bloc Quebecois after Mr Martin's office rejected their demand for an early general election.
The Liberal party became vulnerable after it lost the support of the New Democrats earlier this month following a row over private health care spending.
Their backing had helped Mr Martin's government survive a no-confidence vote in May which he won by a single vote.
If the government falls on Monday, campaigning would take place over the Christmas and New Year holidays.
It would be the first winter campaign since the 1980 poll after Conservative Prime Minister Joe Clark's minority government fell in a confidence vote.
"We don't want to have a Christmas election. We said we would have an election in March. I think that's when it should be," Mr Martin insisted on Sunday.
He succeeded the long-serving prime minister - and his fellow Liberal Party rival - Jean Chretien in December 2003.
Mr Martin was returned to power in a minority government in general elections in June 2004.