Prime Minister Stephen Harper used his annual Stampede barbeque speech to take aim at Liberal Leader Justin Trudeau, who he said has "absolutely nothing of substance to offer" Canadians.

With 15 months to go before an expected federal election, the Prime Minister's folksy message at the Saturday evening riding fundraiser emphasized accomplishments along familiar Conservative themes of economic stability, broadening trade, tough-on-crime legislation and far-from-neutral foreign policy.

Speaking to a crowd of 900, Mr. Harper also referenced April's Quebec election which saw the federalist Liberals win a majority against the Parti Québécois, and suggested a link to his party's governance. He told the 900-person audience that "the gradual decline in Quebec separatist sentiment throughout the stewardship of our government . . . is something that we should take great pride in."

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But most of the key lines of his speech were aimed squarely at Mr. Trudeau, whose party's popularity surged under his leadership. Mr. Harper didn't even mention Official Opposition Leader Thomas Mulcair by name.

While the federal Conservatives have little to fear from Mr. Mulcair's NDP in most of Alberta, Mr. Trudeau maintains his party has the ability to make inroads in the fast-growing province – where the third place party currently has no MPs.

Speaking to Calgary reporters during a Stampede visit to the city on Friday, Mr. Trudeau noted his party's increased share of the vote in the June 30 by-elections in the Alberta ridings of Macleod and Fort McMurray-Athabasca, which Conservative candidates won. In Calgary, where the Liberals haven't won a seat since 1968, Mr. Trudeau is hoping to recruit the chief-of-staff of popular Calgary Mayor Neheed Nenshi to be the party's candidate in a key inner city riding.

"People are more enthusiastically inclined towards the Liberal party here in Alberta than they've been in a long time," Mr. Trudeau told reporters Friday, noting he has travelled to the provincial five times this year.

But on Saturday night, Mr. Harper highlighted Mr. Trudeau's more controversial comments, including that the Boston Marathon bombing perpetrators felt "excluded" from society.

The Prime Minister also said a Liberal government would reverse Conservative tough-on-crime measures, and took aim at Mr. Trudeau's remark earlier this year "the budget will balance itself" with economic growth.

"This guy claims to understand what it's like to be middle-class," Mr. Harper said.

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"Want something from the government? Whatever you want, they'll spend money on it and you can have it. Don't worry about how it'll be paid for. Don't like crime? Just legalize marijuana and, somehow, it will all just go away," the Prime Minister said.

"He has nothing, absolutely nothing of substance to offer."

The Prime Minister also promised the Calgary Southwest riding audience – which also included a number of his MPs from across the country, and Alberta Wildrose and Progressive Conservative MLAs – that the southern Alberta floods in June 2013 won't be forgotten. He noted that his government has been speedy in delivering the first $500 million of disaster aid.

"And there will be more, because the Alberta flood is going to constitute by a country mile the biggest disaster relief package in Canadian history."