Canadian Prime Minister Stephen Harper's Conservative government came under attack Thursday, with three opposition leaders blasting its economic record during the first debate of the Canadian election campaign.

Thomas Mulcair, who leads the left-of-center New Democratic Party (NDP) that has been running neck-and-neck with the ruling Tories in public-opinion polls, accused Harper of having the worst job-creation record since the Second World War.

Canada has lost more than 400,000 manufacturing jobs since Harper took office in 2006, and more than 1.3 million Canadians are unemployed, or 200,000 more than before the country slipped into a recession in 2009, he said during a two-hour televised debate in Toronto.

When Mulcair pointed out that new numbers to be released later this month will likely show Canada is again in a recession, Harper didn't dispute the assertion -- the first time he has made such a public acknowledgement.

The prime minister, who is seeking a rare fourth consecutive mandate, also admitted that falling oil prices have led to "weakness" in the country's energy sector.

However, he also insisted that Canada has out-performed other G7 countries since the global financial crisis, creating 1.3 million net new jobs.

Harper said that only his Conservatives' low-tax plan could help navigate Canada through economic turbulence, "rather than go to a plan of high taxes and high debt and high deficits which is failing everywhere else," as witnessed in Europe.

Liberal leader Justin Trudeau, son of former Prime Minister Pierre Trudeau, said Harper's government has delivered a string of consecutive budget deficits after inheriting surpluses from the Liberal government it defeated nine years ago.

But Green Party leader Elizabeth May, one of only two members of her party to hold seats in the House of Commons in the last Parliament, wasn't as concerned about deficits, saying it was "the wrong time for austerity measures" amid a "weak and shrinking economy."

The debate came just four days after the launch of the longest national election campaign since 1872. Canadians vote for the next federal government on Oct. 19.