The Trudeau Liberals are taking heavy criticism for using their majority power to defeat an NDP motion to establish parliamentary oversight of foreign arms sales.

The motion, also supported by the Conservative Party, was to create a Commons committee that would scrutinize controversial arms exports.

It was proposed as doubts accumulate about the quality of Canada's existing arms-export regime – an approval process that Foreign Affairs Minister Stéphane Dion defended last week after it was revealed he quietly signed permits allowing the bulk of a $15-billion Saudi arms deal to begin flowing to Riyadh.

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The Liberal MPs on the House of Commons foreign affairs committee voted as a bloc Monday evening to sink the NDP proposal by a vote of 5-4. It's the foreign affairs minister who has the power to block or greenlight weapons exports and other countries such as Britain have parliamentary committees that scrutinize arms deals.

NDP Leader Tom Mulcair accused the Liberals of reneging on their campaign promise to bring more transparency to Ottawa.

"They can talk about transparency until the cows come home but they're certainly not practising it," he said.

"How can they possibly justify that? These are members of Parliament who wanted to do their jobs, of getting a report on the human-rights record of countries we'd eventually be exporting to and finding out whether these types of deals should go forward," the NDP Leader said.

"That would have been a good thing if we would have been able to do that in the case of the Saudi arms deal – wouldn't it?"

The lack of information provided by Ottawa on Canada's military trade means Canadians are left largely in the dark over precisely what military and security equipment is being shipped to foreign customers – including those with poor human-rights records. For example, Ottawa has released no information on foreign military sales for any year after 2013.

Conservative foreign affairs critic Tony Clement said his party was prepared to field MPs to staff its share of a subcommittee to scrutinize weapons export deals.

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"It's important that parliamentarians and Canadians have access to the information the government is relying on to make their decision," he said. "The Liberals campaigned on openness and transparency in the last election and they should live up to it."

Bob Nault, the Liberal chair of the Commons foreign affairs committee, accused NDP MP Hélène Laverdière, the motion's sponsor, of playing politics with her proposal.

"Our committee is too high profile and too important to play politics with issues, and we weren't, quite frankly, very impressed that people were trying to seize on one issue when we think it's a lot larger and more complex than that," Mr. Nault said. "To suggest that somehow governments are going to make decisions relating to our relationships with countries based on the whole issue of human rights only – we all know that is not the case."

Asked whether Canada needs a committee to scrutinize arms exports, Mr. Nault said Parliament doesn't need to create "a special committee for every issue that people think needs to discussed." He said concerns over weapons exports can be accommodated by existing committees.

Cesar Jaramillo is executive director of Project Ploughshares, a disarmament group, based in Waterloo, Ont., that is an agency of the Canadian Council of Churches and tracks arms shipments.

"There is a clear need for parliamentary oversight and it's disconcerting, and baffling that the Liberals would miss a clear opportunity to make progress on this front," he said.

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"On arms control, the disconnect between rhetoric and reality just keeps getting wider."

The Liberals are on the defensive after court documents released last week revealed that Mr. Dion, not Stephen Harper's Conservatives, signed the export permits to allow 70 per cent of the transaction to ship to Saudi Arabia, a country notorious for human-rights abuses.

Mr. Dion, it turns out, signed the export permits in early April – shortly after University of Montreal law professor Daniel Turp filed a lawsuit challenging Ottawa's right to export these arms.

The Liberal signature on the export permits means the Trudeau government has taken full ownership of the Saudi arms decision.

Deals to export weapons are not considered to be assured until permits are granted – a process that is the most important step in ministerial oversight of these transactions – and after a careful review of the human-rights situation in the destination country. Last week's export-permit revelation runs counter to Liberal insistence that the Saudi deal was a fait accompli arranged by the Conservatives.

Alex Neve, secretary-general for Amnesty International Canada, called the Liberal decision to defeat the NDP motion to create a parliamentary oversight body on arms exports "a missed opportunity to demonstrate that the commitment to openness and transparency will prevail even with respect to tough and sensitive issues."

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Both Mr. Dion and International Trade Minister Chrystia Freeland have declined to say whether they would have signed the Saudi arms deal in the first place. Mr. Jaramillo suggests that Mr. Dion and Ms. Freeland are reluctant because that would underline how indefensible the decision to carry it through is.