Canada needs a strong Conservative majority to protect trade relations with the U.S., Stephen Harper said Thursday, adding that a border security agreement with the country's southern neighbour is otherwise at risk.

The Conservative leader said that without a Tory government: "The border vision would be dead."

The border agreement signed by Harper and U.S. President Barack Obama earlier this year was meant to support border security while foster trade and economic growth between the two countries.

"One in five Canadian jobs is linked to trade with the United States," said Harper, who was in Niagara Falls to talk about the importance of international trade with the U.S and his commitment to signing new trade agreements.

The deal "will help to strengthen and bolster our trade relationship in order to complete the economic recovery and create jobs."

But the union representing customs and immigration officers slammed Harper on Thursday, saying he has closed local intelligence centres, land-border points of entry and reduced hours of operation.

"The Harper government has previously prioritized effective border security over bureaucratic indifference which is why their acceptance of these counterproductive decisions is so alarming," the Customs and Immigration Union said in a statement.

"Hopefully that leadership will once again be demonstrated in concrete actions and not just words; this is what Canadians deserve."

Harper shifts attack to NDP-led coalition

The Conservative leader also used his pro-trade message to again distance his party from the NDP, saying its opposition to foreign trade deals is "ideological" and its views "have not changed since the Cold War."

"The NDP has opposed every trade deal we have signed," Harper said.

Harper is shifting his campaign message to focus the attack on "an opposition coalition led by the NDP."

Until now, Harper has spent the campaign pitching his Conservatives as the alternative to a coalition of opposition parties led by Liberal Leader Michael Ignatieff.

Harper is continuing to underscore the message that Canada needs a strong majority, but the NDP's late-campaign surge in the polls has apparently forced Harper to change his primary target.

Harper said the choice is still between a Conservative majority government and a minority-led Parliament, which he said would raise taxes and spending.

"That would be such an enormous step backwards, and Canadians need to understand how dramatically different the choices really are when you're looking at two Parliaments, one with a Conservative majority, the other a minority Parliament with a ramshackle coalition led by the NDP that will not last but will do a lot of destruction," Harper said.

Harper also criticized the NDP's plan for a cap-and-trade system, saying their proposal would hike up prices at the gas pumps

"The NDP proposes $20 billion in carbon taxes," he said. "That's at least 10 cents a litre in gasoline and big increases in every other consumer good."

Harper appeared to be referring to figures quoted by economist Jack Mintz, who tweeted on Thursday that an "NDP cap-and-trade at $40 per carbon tonne will be a 10 cent hike in gas tax."

Later, Mintz stood by his calculations after a Globe and Mail story said his figures were based on the wrong assumption that the NDP would include the fossil fuels that consumers use.

"Cap and trade on refining will surely increase gas prices. Let's get realistic," Mintz tweeted.

Meanwhile, Layton shot back that gas companies are gouging Canadians, and that Harper has done nothing to stop it.

He suggested toughening up competition laws and establishing a special ombudsman to to put pressure on oil companies.

"We want to start with the competition law," Layton said. "That's what we want to start with because it's not being adequately used. Mr. Harper clearly has no desire to go after the oil companies. He's too busy giving them subsidies."

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NDP Leader Jack Layton poses with Jacq Brasseur at a campaign stop in Yellowknife on Thursday (Andrew Vaughan/Canadian Press)

Recent public opinion polls have shown that the Conservatives and the Liberals are both losing support to the NDP.

The NDP has moved into second place in most national polls behind the Conservatives.

That change has also caused the Liberals to aim their sharpest critiques at the NDP.

Even former prime minister Jean Chrétien used his speech on Wednesday  to take a jab at the NDP.

"And I checked the program of the NDP," the former prime minister said.

"Nobody had read it until a few days ago. Apparently it's not adding up."

With files from The Canadian Press