Prime Minister Stephen Harper greets employees during a visit to the Héroux-Devtek plant on Friday. He accused the Liberals of playing politics over the government's purchase of F-35 fighter jets. (Ryan Remiorz/Canadian Press

Prime Minister Stephen Harper has mounted an aggressive, campaign-style defence of his government's multibillion-dollar F-35 fighter jet purchase in the heart of Quebec's aerospace industry.

In separate addresses to employees and executives on Friday at aerospace facilities in the election battleground province, Harper said it is "incredible" Liberal Leader Michael Ignatieff would threaten to cancel a project that would bring jobs to Quebec's aerospace industry for "a generation."

The prime minister called on the provinces aerospace workers to "make your voices heard" over the Liberals' threat to cancel the contract.

"I find it sad that some in Parliament are now backtracking and talking about cancelling contracts," Harper said. "We have to take opposition threats to cancel these contracts seriously. They have done it before … and they will do it again unless you make your voices heard."

The prime minister's appearance in Quebec comes amid increased speculation about a spring federal election.

Harper denied his appearances were aimed at bolstering the Tories' chances in ridings in and around Montreal in a potential spring vote. He hit out again at what he said was an attempt by opposition parties to trigger an "opportunistic election" while Canadians want their politicians to focus on job-creation and Canada's fragile economic recovery.

The F-35 contract, one of the biggest military equipment purchases in Canadian history, is worth $9 billion, but the full cost could rise to as much $18 billion once the government signs a maintenance contract.

The fighters would replace Canada's fleet of CF-18s, which recently underwent a $2.6-billion upgrade. The CF-18s are expected to reach the end of their operational life by 2020.

Ignatieff's Liberals have questioned the cost estimates for the F-35s that have risen exponentially in recent years, as well as decried the lack of a competitive bidding process for the contract.

But Harper said his Liberal predecessors, Jean Chrétien and Paul Martin, chose to invest in the F-35 "because they believed it was best aircraft for Canada."

The F-35 purchase is worth $9 billion, but the full cost could rise to as much $18 billion once the government signs a maintenance contract. (Defence Department/Canadian Press)

"We supported it because we believed it was the right thing to do," he said.

Harper compared the current resistance to the Liberals' 1993 cancellation of the EH-101 helicopter contract — which he said backfired at the time and cost taxpayers nearly $500 million in cancellation fees. The government says Canadian aerospace companies stand to benefit from the projected $12 billion in service contracts the program is expected to bring.

Senator Larry Smith, the former CFL commissioner and current Conservative star candidate in the West Island riding of Lac-Saint-Louis, was not at Friday's events, but the Tories hope he can win the party its first Montreal seat in decades.

With files from The Canadian Press