Prime Minister Stephen Harper ramped up his criticism of Justin Trudeau, delivering a stinging attack on the Liberal leader during a pep talk to Ontario Conservatives.

In a speech at the Canadian Warplane Heritage Museum in Hamilton on Thursday night, Harper took aim at several of Trudeau's past statements, from terrorism to China.

He noted neither the Liberals nor the New Democrats have supported his government's law and order reforms.

Harper accused the opposition parties of believing criminals are victims of society.

He referred to Trudeau's reaction to the 2013 terrorism attack at the Boston Marathon when the Liberal leader said governments must look at the root causes of homegrown terrorism.

Harper also alluded to opposition criticism of his government's handling of foreign policy, referring to a comment Trudeau once made about admiring China and asked how many Canadians want to live there.

"My point is that Justin Trudeau didn't really want to answer that question because the answer is too obvious," Harper said.

"The best country and the best government in the world is Canada's!"

Gun owners now safe from 'bureaucrats'

Trudeau was criticized last year when he was asked which country he admires the most and replied China because having a dictatorship can allow it to turn the Chinese economy around "on a dime."

Harper also reached out to gun owners, apparently alluding to a recent decision by the RCMP to ban a previously legal rifle, the Swiss Arms Classic Green carbine.

Harper said it's completely unacceptable that owners of the weapons should be subject to an "arbitrary stroke of a bureaucrat's pen."

"We have ensured owners of those guns will not face prosecution," Harper said.

"We will take all actions necessary to ensure bureaucrats cannot bring back the long-gun registry through the back door!"

The government said in July it would review the RCMP's decision and was exploring a number of options.

The National Firearms Association estimated there are 1,000 to 1,800 of the rifles in Canadian hands.