The Liberal Party will scrap the Conservatives' troubled F-35 fighter jet program should they assume government, Leader Justin Trudeau announced in Halifax today.

"Our Canadian Forces are in a state of stagnation," Trudeau said to a crowd of supporters at Pier 21 in Halifax, home to the Canadian Museum of Immigration.

In its place, the Liberals said they would launch an "open and transparent competition" to buy more affordable planes to replace Canada's aging CF-18 jets. Trudeau said the money saved by scrapping the F-35 procurement would go primarily to increasing spending on the Royal Canadian Navy.

The primary mission of our fighter aircraft, Trudeau said, is the defence of North America.

Expanding the procurement process for the navy will be a priority, Trudeau said. That includes acquisition of search-and-rescue ships, icebreakers and surface combatants.

He said he would keep the Conservative promise to build Arctic offshore patrol ships originally announced in 2007, and which were due in 2013. The plan was to build as many as eight ships.

In January, the government finally signed a contract guaranteeing delivery of only five of the vessels (and a possibility of a sixth), with the first scheduled for delivery in 2018.

"We are committed to the initial promise of making sure there's at least six ships go through the Halifax shipyards," Trudeau said.

The Liberal leader did not offer a specific number when asked how much today's promises would cost, instead saying that it would save "tens of billions of dollars in the coming decades."

Tories not abandoning fight against ISIS

Conservative Leader Stephen Harper, meanwhile, said that the government — and even previous Liberal governments — have had need of Canada's military assets around the world.

"[Trudeau] has indicated that we do not need that capacity in our air force. I don't know where he's getting his information," Harper said during a rally in Windsor, Ont.

"We along, with our allies, have been using this exact capacity with our current CF-18s in various parts of the world, including right in the fight against ISIS in Iraq and Syria," he said.

Conservative leader Stephen Harper responds to Liberal leader Justin Trudeau's proposal to scrap the plan to replace aging CF-18 fighter jets. 0:57

"We are not going to abandon our fight against ISIS, not going to abandon our allies, not going to abandon people in the region, not going to abandon that kind of capacity in our air force and we are not going to abandon our domestic aerospace industry."

The Liberal leader, for his part, repeated a promise to end Canada's combat mission against ISIS if he becomes prime minister in the Oct. 19 vote.

F-35 controversy

The F-35 program has been embroiled in controversy since the Conservative government announced its intention to purchase the fighter jets in 2010.

The Conservative government had planned on purchasing 65 F-35s for the Royal Canadian Air Force but the procurement process was put on hold after the auditor general accused the government of fudging the project's costs and not doing sufficient research. A 2012 report had lambasted the military's opaque purchasing process.

The purchase would have cost taxpayers an estimated $44 billion over its four-decade lifetime.

A June 2014 report from the Canadian Centre for Policy Alternatives said buying the single-engine F-35s would be a "serious mistake."

More recently, CBC News reported that the widening fallout from the botched program may be damaging the military's relationships with its international allies.

Trudeau said the Liberals would maintain current defence spending levels and would review the Canada First Defence Strategy.

He outlined, too, a zero-tolerance policy for sexual harassment in the military, adequate mental health support and services and "high-quality" career counselling and support "to protect the well-being of the men and women in uniform, both while in service and afterwards."

The Liberal leader also repeated a promise to reopen the nine Veterans' Affairs offices that were shuttered by the Conservative government in early 2014.