Most Canadians oppose the decision of some Conservative MPs to appear in the U.S. media criticizing the federal Liberals' $10.5-million payout to Omar Khadr, according to a new Nanos survey.

Conservative MPs have been expressing outrage over Prime Minister Justin Trudeau's decision to approve the multimillion-dollar payment, which settled Mr. Khadr's $20-million civil lawsuit against the government over violations of his rights as a Canadian citizen.

Liberal ministers said last month that the government had little chance of winning the lawsuit and would likely have had to pay millions more in compensation and legal costs if it continued with the case.

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Read more: Conservatives mount campaign against Trudeau over Omar Khadr settlement

Some Conservative MPs took the extra step of sharply criticizing the Liberal government in American news outlets. Foreign affairs critic Peter Kent wrote a column for The Wall Street Journal titled "A terrorist's big payday, courtesy of Trudeau," while Conservative MP Michelle Rempel told Fox News host Tucker Carlson on air that "most Canadians are absolutely outraged about this."

When asked for their opinion on the decision of federal Conservative MPs to criticize the Khadr payment in the U.S. media, more than six out of 10 Canadians said they feel uncomfortable or somewhat uncomfortable about the actions of the Conservative MPs.

"Going south to attack the Liberal government was definitely not a growth strategy," said pollster Nik Nanos, noting that separate polling by Nanos shows a decline in support for the Conservative Party in recent weeks as the party focused on the Khadr decision.

"For some, it might be the right message, but it's definitely in the wrong format and the wrong place and I think that's where the Conservatives are vulnerable on this," he said.

Nanos' tracking of voting intentions had support for the Conservatives at 28.6 per cent when Andrew Scheer was elected by members as the new leader of the party on May 27. The party's support then climbed to 33 per cent in early July before falling back to 29.1 per cent at the end of the month.

During that same period, support for the Liberals has declined from 40.34 per cent in a May 26 poll to 36.7 on July 28. Support for the NDP rose from 16.72 per cent in late May to 20 per cent in late July.

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"What we've seen is that [the Conservatives] have reversed the momentum that they created after their leadership with their focus on Omar Khadr," said Mr. Nanos.

Further, about half of Canadians surveyed said they believe that openly criticizing the decision to pay Mr. Khadr $10.5-million in the U.S. media will have a negative or somewhat negative impact on Canada-U.S. relations.

The findings in relation to the Conservatives and Mr. Khadr are based on a hybrid phone and online survey of 1,000 Canadians that included a mix of land and cell lines. It was commissioned by The Globe and Mail and conducted between July 23-26 as part of an omnibus survey. The margin of error for a random survey of 1,000 Canadians is plus or minus 3.1 percentage points, 19 times out of 20.

The party support numbers are based on a four-week rolling sample comprised of 1,000 interviews in total, with 250 new interviews conducted each week.

Mr. Khadr, who grew up in a family with close ties to al-Qaeda founder Osama bin Laden, was accused of killing an American soldier in Afghanistan when he was 15 during a 2002 battle. He was then imprisoned at the U.S. detention facility in Guantanamo Bay for 10 years.

Mr. Khadr pleaded guilty in 2012 to killing U.S. Delta Forces Sergeant Christopher Speer so he could be moved to a Canadian prison. He later recanted the confession and is appealing the U.S. conviction.

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A 2010 Supreme Court of Canada ruling said agents of the Canadian Security Intelligence Service "offended the most basic Canadian standards of detained youth suspects" by participating in abusive U.S. interrogations of Mr. Khadr at Guantanamo.

Mr. Kent said he had "no regrets" about raising the Khadr payment in the U.S. media. In an e-mail, he said he has received positive feedback from constituents of all political persuasions that the issue was worthy of North American discussion.