harper canada
Canada's Prime Minister Stephen Harper takes part in a news conference at Rideau Hall after asking Governor General David Johnston to dissolve Parliament, beginning the longest federal election campaign in recent history, in Ottawa August 2, 2015. Reuters/Blair Gable

Canadian Prime Minister Stephen Harper on Sunday called a parliamentary election for Oct 19, kicking off a marathon 11-week campaign likely to focus on a stubbornly sluggish economy and his decade in power.

Polls indicate that Harper's right-of-center Conservative Party, which has been in office since 2006, could well lose its majority in the House of Commons.

That would leave Harper at the mercy of the two main center-left opposition parties, who could unite to bring him down. Minority governments in Canada rarely last more than 18 months.

Harper, 56, says only he can be trusted to manage an economy that is struggling to cope with the after-effects of a global economic slowdown and a plunge in the price of oil, a major Canadian export.

Opposition parties say Harper has mishandled the economy and should boost government spending, a move he says would spark a crisis like the one ravaging Greece.

Harper announced the election after visiting Governor General David Johnston - the representative of Queen Elizabeth, Canada's head of state - to formally request the dissolution of parliament.

"Our well-being depends on the economy and the wrong leader will do real harm," he said.

"Now is not the time for the kinds of harmful economic schemes that are doing so much damage elsewhere in the world."

Polls show the Conservative are slightly trailing the left-leaning New Democrats (NDP), who have never governed Canada. The Liberals of Justin Trudeau are well behind in third.

Both parties say Canada needs a change from Harper, who has cut taxes, increased military spending, toughened the country's criminal laws and streamlined regulations governing the energy industry.

Ipsos Public Affairs pollster John Wright said the race was "very competitive" and chances of the Conservatives winning any kind of government were 50 percent, down from 88 percent last year.

Data released on Friday showed gross domestic product shrank in May, the fifth decline in a row. The figures suggest the economy was likely in a technical recession in the first half of 2015.

Five of Canada's last six election campaigns have lasted the minimum length of just over five weeks.

The Conservatives have deep pockets and the campaign - the longest in modern Canadian history and the third longest on record - will benefit their chances as it will allow them to run a wave of attack ads. Opposition parties say this is an abuse of the system.

(With additional reporting by Jeffrey Hodgson in Toronto; Editing by Diane Craft and Raissa Kasolowsky)