OTTAWA (Reuters) - The leak of information about Barack Obama’s position on the North American Free Trade Agreement was “blatantly unfair” to his campaign, Canadian Prime Minister Stephen Harper said on Wednesday.

Canada's Prime Minister Stephen Harper speaks during Question Period in the House of Commons on Parliament Hill in Ottawa March 5, 2008. REUTERS/Chris Wattie

Harper said the government was mounting an “internal security investigation” to find out who leaked the information, which suggested Obama’s campaign had said not to pay too much attention to his protectionist rhetoric on NAFTA.

“This kind of leaking of information is completely unacceptable and in fact ... it may well be illegal,” the prime minister told Parliament.

“It is not useful, it is not in the interests of the government of Canada, and the way the leak was executed, Mr. Speaker, was blatantly unfair to Sen. Obama and his campaign.”

Obama’s rival in the U.S. Democratic primaries, Hillary Clinton, had seized on the Canadian information to try to demonstrate that Obama could not be trusted on foreign affairs and that he said one thing in private and another in public.

The issue arose when Obama and Clinton said in a debate last week they would threaten to pull out of NAFTA -- which joins the United States, Canada and Mexico as trading partners -- unless its environmental and labor standards are renegotiated.

Shortly after, a memo circulated that was written by a Canadian diplomat after a February 8 meeting in Chicago with Obama economic adviser Austan Goolsbee.

“He (Goolsbee) was frank in saying that the primary campaign has been necessarily domestically focused, particularly in the Midwest, and that much of the rhetoric that may be perceived to be protectionist is more reflective of political maneuvering than policy,” the memo read.

On Monday afternoon, on the eve of the Democratic primaries in Texas and Ohio, the Canadian government issued a formal statement regretting any inference that Obama was taking a different position in public from views expressed in private.

U.S. Sen. Sherrod Brown, an Ohio Democrat, said the flap probably had only a minor effect on the outcome because both candidates were offering a welcome change on trade policy.

“The Canada thing was much ado about nothing, I think, to most voters,” he said in a call with U.S.-based reporters.

Leo Gerard, president of the United Steelworkers Union, said he agreed with Brown. But Lori Wallach, director of Global Trade Watch, part of the Washington-based advocacy group Public Citizen, said it may have helped stop Obama’s momentum.

Obama was 24 points behind Clinton when he started campaigning in Ohio and managed to close much of that gap, partly by criticizing her for supporting NAFTA when her husband, Bill Clinton, was president, Wallach said.

The memo helped “blur the distinction” that Obama was trying to make between himself and Clinton on NAFTA and may help explain why he stopped rising in the polls shortly before the vote in Ohio, she said.

In Ottawa, Jack Layton, leader of the opposition New Democratic Party, said the leak had damaged relations with the United States, and he even asked Harper to call in the Royal Canadian Mounted Police.

Harper said the clerk of the Privy Council -- Canada’s top civil servant -- was handling an internal security investigation.

“Based on what they find and based on legal advice, we will take any action that is necessary to get to the bottom of this,” Harper said during the daily Question Period in the House of Commons.

International Trade Minister David Emerson said on Wednesday he did not believe Obama would just abandon NAFTA.

“I’m sure if Mr. Obama were the president he would look after the best interest of the United States,” Emerson said when asked by reporters. “I just do not believe for a moment, not a nanosecond, that walking away from NAFTA is in the greater interests of Americans. When they get down into that, it’ll become pretty clear.”