Canada's prime minister has called general elections for October 19, kicking off a campaign for a fourth straight term in power for the Conservatives.

Stephen Harper, in office since 2006, dissolved parliament after holding a meeting on Sunday with Governor-General David Johnston, the representative of Queen Elizabeth II, Canada's nominal head of state in this Commonwealth country.

Voters will be choosing all 338 members of the House of Commons, 30 more than in the last election because of redistricting.

It's an election about who will protect our economy in instability and ensure Canada's future prosperity. The national election is not a popularity contest.

Stephen Harper, Canada PM

Polls suggest the race will be tight.

Harper said the election was about "leadership on the big issues that affect us all, our economy and our nation's security".

"It's an election about who will protect our economy in instability and ensure Canada's future prosperity. The national election is not a popularity contest," he said.

The economy is expected to be declared officially in recession in September when second quarter GDP figures are released.

However, Stephen Poloz, the central bank governor, has already said this month that the economy is in recession. 

Harper had planned to present himself as one of the first G7 leaders to post a balanced budget since the global financial crisis, bolstering his image as a strong fiscal manager.

Analysts say the opposition New Democrats, led by Tom Mulcair, 60, have a chance to gain power after the party won control of the legislature in Alberta, Canada's most conservative province, a few months ago.

"Canadians are telling us that they want change. After 10 years of Stephen Harper in Ottawa they want to turn the page," Mulcair said.

Justin Trudeau, the Liberal leader and son of Pierre Trudeau, the late prime minister, is also in the running to be the next prime minister. But he has trailed in recent polls after Conservatives have run repeated attack ads saying the 43-year-old is not ready for the job.

The first televised debate is this Thursday and is seen as a key test for Trudeau.

Former colleagues of Harper say his long-term goals are to kill the once widely entrenched notion that the Liberals - the party of long-time leaders Trudeau and Jean Chretien - are the natural party of government in Canada, and to redefine what it means to be Canadian.

The Green Party and the Bloc Quebecois are also in the race.

The 79-day campaign will be one of the longest in Canadian history.

Source: Agencies