Stephen Harper spoke out in favour of keeping the United Kingdom in one piece Wednesday during a visit to London where he was asked about a looming vote on Scottish independence.

The Canadian Prime Minister was in London to tout trade ties between the U.K. and Canada but was asked how the United Kingdom might save its political union. A vote by the Scottish will take place later this month and a recent poll suggests the Yes and No sides are only about six percentage points apart among decided voters.

Mr. Harper questioned what breaking up the United Kingdom or Canada, for that matter, would do to resolve any of the major problems common to western industrialized countries, including job losses to developing countries, strained social service programs or terrorism, climate change and the threat of pandemics.

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"What would the division of a country like Canada or the division of a country like the United Kingdom do to advance any solutions to any of those issues?" Mr. Harper asked.

"We think from a Canadian perspective that a strong and United Kingdom is an overwhelmingly positive force in the world and that there's nothing in dividing those countries that would serve either greater global interests or frankly the interests of people in those countries."

A U.K. journalist posing questions to Mr. Harper joked it was a shame he couldn't go north to Scotland to speak on the matter but the Prime Minister quipped that he "might not be so well received there." The Prime Minister prefaced his remarks by saying ultimately that Scotland's future in the United Kingdom "is ultimately a decision for the Scots" but proceeded to argue against breaking up the U.K.

In remarks that appeared to have been prepared in advance, Mr. Harper cautioned both sides in the Scottish independence debate to be prepared to live with the consequences of the referendum, which is set for September 18.

"The decision has to be respected and it has to be taken seriously," Mr. Harper said.

"This is a vote with immense consequences and those consequences should be thoroughly understood and digested and the public, particularly the establishment, should be more than willing to accept the judgment that ordinary people will, rightly or wrongly, deliver. I don't think there's any way of soft pedalling that," he said.

"It's momentous and should be treated as such by all sides."

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At one point the Prime Minister joked that he's biased on the matter because of his heritage. "I am mainly English on my father's side and mainly Scottish on my mother's side so union has worked well for me," Mr. Harper said.

He said Canada is spared a similar debate these days and noted the recent defeat of the separatist Parti Québécois government in Quebec.

"Fortunately in Canada we don't have to talk about it much," Mr. Harper said.

"We just had an election in the province of Quebec where we had the strongest outcome for federalism in over 40 years. I don't want to say the issue is resolved, one can never say that, but certainly the trajectory has been very good."

Mr. Harper said he believes Canadians have trouble relating to the debate over Scottish independence because these two cultures "are so completely integrated in Canada that the idea of separating English people from Scottish people in Canada is almost inconceivable."

Turning to Quebec, Mr. Harper suggested younger Quebeckers, including those who voted in the recent provincial election to turf the Parti Québécois, do not see separation from Canada as a solution to pressing problems.

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He said that an intense debate among Quebeckers created a divided society for many years.

"I do believe at some point, people, particularly the younger generation, started to sit back and say the following things: we've been having this existentalist debate for 40 years and what is the resolution of this debate going to do about the things that actually matter in my life," he said.