Prime Minister Stephen Harper has fired one shot at Sri Lanka and another across the bow of Commonwealth friends, confirming he will boycott next month's leaders' summit and threatening to cut off funding to the organization.

Mr. Harper is the only leader in the Commonwealth – the 54-nation organization of countries once part of the British empire – who will skip the November summit to protest against the host's human-rights record, although he has hinted at his plans for two years.

But he made a new threat by asserting he will reconsider Canada's substantial funding for the group – intensifying a dispute fuelled by frustrations with the Commonwealth and its secretary-general, Kamalesh Sharma. Mr. Harper's special envoy to the Commonwealth, Senator Hugh Segal, accused the organization's secretariat of acting as a "shill" for Sri Lanka's government.

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At the Commonwealth summit in Perth, Australia, two years ago, Mr. Harper warned he would boycott this year's meeting in Colombo unless Sri Lanka's government made progress on reconciliation with the Tamil minority and showed accountability for abuses at the end of the country's civil war in 2009.

On Monday, at the APEC summit in Indonesia, he said democratic freedoms have eroded in Sri Lanka under President Mahinda Rajapaksa, including the impeachment of the country's chief justice and the killing and jailing of opponents and journalists.

"In the past two years, we have not only seen no improvement in these areas, in almost all of these areas we've seen a considerable rolling back, a considerable worsening of the situation," Mr. Harper said at the APEC summit site.

MP Deepak Obhrai, parliamentary secretary for Foreign Affairs Minister John Baird, will represent Canada at the Commonwealth summit.

In Ottawa, Sri Lankan High Commissioner to Canada Chitranganee Wagiswara said the announcement "did not come as a surprise," and noted that most other leaders will attend. She said Sri Lanka's government rejects the allegations of human-rights abuses, and argues it has made progress.

Others, including the United States, have echoed Mr. Harper's criticisms. However, Mr. Harper has led a high-profile campaign. Sri Lanka's government often says Canada is motivated by domestic concerns because of its 300,000-strong Tamil minority. Mr. Segal said he has not been lobbied by Canadian Tamil groups.

"The one party they never vote for would be us," said Mr. Segal, a Conservative. "Their vote tends to be somewhere between the NDP and the Liberals. The notion that we're playing for some diaspora political game is a creation of our friends of Sri Lanka."

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Mr. Harper's threat to review Commonwealth funding could be of greater concern. Canada provides $5-million a year for the organization's secretariat, about 20 per cent of its budget, and another $15-million for programs.

In 2011, Canada attempted to push a values charter for the Commonwealth and mechanisms to isolate members who violated it – but the organization delayed some proposals, rejected others, then passed a watered-down version late last year.

The Canadian government viewed Mr. Sharma as unhelpful in that battle, and in the effort to call Sri Lanka to account. Mr. Segal said Ottawa has been waiting for the "secretariat to engage not as a shill for the Sri Lankan government, but as an agent of the Commonwealth." He accused Mr. Sharma of hiding from Commonwealth ministers the damning legal opinions that he had commissioned on the impeachment of Sri Lanka's chief justice.

He said Canada's concern is not just that Mr. Rajapaksa will be host, but chair of the Commonwealth for two years.

But some think the Prime Minister's boycott of the summit will miss the mark.

Bruce Levy, who was Canada's high commissioner to Sri Lanka until last year, is worried about the erosion of democracy in Sri Lanka, and that rights are "going backwards." But he said that for a long time, the Canadian government appeared to Sri Lankans to focus on abuses of Tamils, rather than the general deterioration under the Rajapaksa regime, allowing the Colombo government to portray Canada as "being rigidly obsessed with a single issue, and captive to a single lobby."

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That may be easier if Mr. Harper is the only leader skipping the Commonwealth meeting, he said, and it might have been better to go to Sri Lanka to meet human rights advocates.

"I'd like Canada to be an effective voice, and not just a headline voice," he said.

With a report from The Canadian Press