The federal Conservative government has been defeated on a historic vote in Parliament, setting the stage for a May election.

MPs voted 156-145 in favour of a Liberal motion today citing Stephen Harper's minority Tories for contempt of Parliament and expressing non-confidence in the government.

The contempt charge marks a first for a national government anywhere in the Commonwealth.

Harper emerged from the House of Commons after the vote and announced he will visit the Governor General's residence Saturday morning to dissolve the 40th Parliament and sound the starting gun on an election campaign. It will be the fourth election in seven years.

The prime minister gave a preview of his campaign message, accusing the opposition of forcing an election Canadians don't want, and defending this week's federal budget as a responsible plan during a fragile economic recovery.

He is expected to campaign on the budget, which was laden with tightly targeted tax credits and riding-specific goodies, while simultaneously accusing his opponents of plotting to form a coalition government if he fails to win a majority.

"There was nothing -- absolutely nothing -- in the budget that the opposition could not or should not have supported," Harper said.

"Unfortunately, Mr. Ignatieff and his coalition partners in the NDP and the Bloc Quebecois made abundantly clear that they had already decided they wanted to force an election instead."

But Liberal Leader Michael Ignatieff insisted there can be no more profound cause for an election than the protection of democracy.

"There are only two alternatives here," he said. "More of this disrespect for democracy, more of this contempt for the Canadian people, or a compassionate, responsible Liberal government."

He said Liberals will fan out across the country "to present a message of hope instead of a message of fear, a message of unity instead of a message of division, a message of principle instead of the constant politics of personal destruction."

Commons Speaker Peter Milliken and an opposition-dominated committee had already found a case for contempt, and the Liberals ensured that would be the trigger for the defeat of the government 29 months after the last election.

The opposition parties wasted no time pounding home their campaign message, slamming the prime minister as a secretive leader who abuses power and leads a government plagued by scandal.

In the past month, the Conservative party and four of its top officials have been charged with election overspending and two RCMP investigations have been launched against former political staffers.

Ignatieff acknowledged that some Canadians are questioning the need for another election.

"We did not seek an election," he said. "But if we need one to replace a government that doesn't respect democracy with one that does, I can't think of a more necessary election."

The NDP said the budget fails to deliver real relief to beleaguered seniors, understaffed health-care systems, and middle-class Canadians burdened by home heating fuel taxes.

NDP Leader Jack Layton was still imploring the government to rewrite its budget as late as Friday morning's final question period in the House.

"They're just plain stubborn," said Layton. "Why are Conservatives intent on provoking an election?"

Prospective voters have been bombarded with $26 million worth of feel-good Economic Action Plan ads over the past 11 weeks and bureaucrats were directed late last year to start using the "Harper Government" in place of Government of Canada on departmental news releases.

And taxpayer-funded ads from the Finance Department warned of the "fragile" nature of the economic recovery.

The government's economic message has been paired with dire warnings of a Liberal-led coalition threat.

Ignatieff has tried to polarize the coming election into a two-party fight between Harper Conservatives and those who oppose them -- between "a blue door and a red door."

Conservatives are trying to convince Canadians otherwise.

"Lurking behind the red door are socialists and separatists plotting for cabinet seats!" thundered MP Dean Del Mastro in the Commons.

The alarmist Conservative talk was scoffed at by Bloc Leader Gilles Duceppe, who has pointedly noted that Harper proposed defeating Paul Martin's minority Liberal government on its throne speech in 2004 and replacing it, with NDP and Bloc backing.

Duceppe revelled in the details this week, describing the Delta Hotel on Maissonneuve Boulevard in Montreal where Harper convened the conspirators.

"He was coming in my office saying, 'If Martin is going to lose confidence, what do you want in the throne speech? What would you like in the budget?"' Duceppe recalled.