Mr Harper's minority government has needed opposition support to pass bills
Canadian Prime Minister Stephen Harper has called an early election for 14 October in a bid to strengthen his minority Conservative government.
He met Governor General Michaelle Jean - the representative of Canada's head of state, Queen Elizabeth II - to request the dissolution of parliament.
The latest polls indicate the Conservatives are ahead of the opposition Liberals.
The PM, elected in 2006, has complained that parliament is deadlocked.
The vote will be Canada's third national election in four years.
Mr Harper's government has needed the support of the main opposition parties, the Liberals and the Bloc Quebecois, to pass legislation and adopt budgets.
The election call had been widely expected, with Mr Harper complaining in recent weeks that parliament was "dysfunctional".
Holding the election this year breaks Mr Harper's own fixed-date election law, something he had said was necessary to prevent prime ministers calling elections when polls indicated they were in a favourable position.
Mr Harper has made it clear he is running on economic issues and criticised the Liberals' plan to tax greenhouse gas polluters while cutting other taxes.
"Between now and October 14, Canadians will choose a government to look out for their interests at a time of global economic trouble," Mr Harper said in a statement.
"They will choose between direction or uncertainty; between common sense or risky experiments; between steadiness or recklessness."
The opposition leaders are expected to make their own addresses later on Sunday.
Mr Harper led the Conservatives to victory in the 2006 election, ending 12 years of Liberal government.
The party heads into the election with 127 of parliament's 308 seats. The Liberals have 95, the Bloc Quebecois has 48 and the New Democratic Party (NDP) 30.
There are three Independent MPs, the Green Party has one seat and four are vacant.
Opposition Liberal leader Stephane Dion proposes taxing polluters
An opinion poll held last week suggested support for the Conservatives had grown over the summer.
The Environics survey suggested that 38% of Canadians would vote for the Conservatives; 28% for the Liberals; 19% for the NDP, eight for the Bloc Quebecois and seven for the Greens.
The figures put the Conservatives within striking distance of a majority government, Donna Dasko, senior vice-president of Environics Research Group, told CBC News.
The leader of the separatist Bloc Quebecois, Gilles Duceppe, said his party was best positioned to stop the Conservatives gaining a majority.
The same Environics poll indicated increased support for the Conservatives in Quebec, where separatist ardour has faded in recent years.
Liberal leader Stephane Dion is staking his command of the party on his "Green Shift" plan, which would tax polluters but reduce other taxes.
If his party does not do well on 14 October, his leadership will likely come under scrutiny at a party convention in December.
Mr Dion has described Mr Harper as Canada's most right-wing prime minister in history.
Mr Harper supported the Iraq war while in opposition and withdrew Canada from the Kyoto Protocol that aims to cut greenhouse gases. He has also increased Canada's troop commitment to Afghanistan.