The Trudeau government is facing accusations it misrepresented the $15-billion Saudi arms deal to Canadians as the Liberals play down their unexpectedly large role in green-lighting exports of these weaponized armoured vehicles to a country notorious for human-rights abuses.

As The Globe and Mail first reported, Foreign Affairs Minister Stéphane Dion only last week quietly approved export permits covering more than 70 per cent of the transaction with Saudi Arabia – a decision that represents the most vital step in determining whether a weapons shipment to a foreign country can proceed or whether it's "illegal," as Ottawa calls it.

NDP Leader Tom Mulcair on Wednesday said the Liberals misled Canadians. "I am going to say this straight up and I don't say it lightly: The government lied to Canadians about who signed what [and] when in the Saudi arms deal and that is a very serious matter," he said. "The Liberals lied."

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Mr. Dion held a brief news conference Wednesday to defend his rationale for approving the permits. He noted all major political parties said they would respect the contract during the 2015 election and said Ottawa has seen no evidence that any of the light armoured vehicles Canada previously sold to Riyadh were misused.

"Our best and regularly updated information indicates that Saudi Arabia has not misused the equipment to violate human rights nor has the equipment been used in a manner contrary to the strategic interest of Canada and its allies," Mr. Dion said.

The revelation that Mr. Dion approved the bulk of this deal runs contrary to the Liberal claim that the Saudi export deal was a fait accompli. Many observers had assumed the Conservatives had granted export permits. It also makes the Trudeau government more squarely responsible for a deal with a country increasingly cast as a pariah when it comes to human rights. The Harper Tories inked the deal in 2014 but approved only the export of technical data about the vehicles to Riyadh.

News of the permit approvals came to light after University of Montreal law professor Daniel Turp filed a lawsuit trying to block the combat-vehicle shipments to Saudi Arabia and sought a copy of the export permits. In response, the Department of Justice released a memorandum stamped "Secret," which Mr. Dion signed just weeks after Mr. Turp's legal action was filed, authorizing the bulk of the Saudi deal.

Mr. Turp's challenge has prompted a reaction from General Dynamics Land Systems, the London, Ont.-based defence contractor building the armoured vehicles for the Canadian government, which is the prime contractor in this deal. A lawyer working on behalf of General Dynamics registered with the federal lobbyist registry this month to arrange meetings with the Department of Justice over the Turp lawsuit.

On Wednesday, Liberals answered the accusation they misled Canadians by emphasizing that the 2014 contract signed under the Harper government was too costly to break.

"The fact is there are jobs in London relying on this. Commitments have been made to the world that we will honour our good name when we sign our contracts," Prime Minister Justin Trudeau told the Commons.

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Mr. Dion's office played down the significance of the export-permit approvals. "The permits are an administrative process with respect to the contract – a done deal under the previous Conservative government," Joseph Pickerill, director of communications for Mr. Dion, said in an e-mail.

Weapons-control experts disagreed, saying the decision to award permits for weapons shipments is central to whether an export proceeds. The federal Canadian Commercial Corporation signs a great number of foreign deals for military shipments on behalf of Canadian companies but these contracts do not allow a deal automatic progress through the export-control process, they say. The permitting stage is where Ottawa is supposed to bring its most stringent scrutiny to bear and consider, for instance, what observers describe as a deteriorating human-rights situation in Saudi Arabia.

"The Minister of Foreign Affairs is responsible by law for the authorization or denial of military export permits," said Ken Epps, a researcher for Project Ploughshares, an anti-war group that tracks weapons shipments. "This is not merely an administrative procedure, but rather, lies at the core of the oversight and control of Canadian arms exports. To downplay the importance of this role does a disservice to Canadians who are concerned about where Canadian weapons are shipped and how they may be misused."

Federal arms-control officials drive the same point home in e-mails obtained and published by The Globe and Mail last year, where they tell Global Affairs colleagues there were no assurances the $15-billion transaction was approved until export permits were processed. In 2014, the department undertook an initial review of the deal to check for "red flags." It found none but Debbie Gowling, a senior official in the export-controls division, reminded the department there was no guarantee the sale was officially approved by Ottawa until permit applications were scrutinized.

It's these export-permit applications that Mr. Dion approved on April 8, which means it was the Liberal minister's decision to ultimately sanction the export of arms to a country ranked by Freedom House as "among the worst of the worst" on human rights.

In his news conference, Mr. Dion repeated what he said as far back as January, that he could rescind, suspend or revoke permits should Canada become aware of human-rights violations conducted by the LAVs.

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Mr. Epps pointed out the bulk of the exports appear set to ship to Saudi Arabia over four years. That means Canada would have no leverage after that.

Mr. Dion warned of financial penalties if the Liberals break the contract but the federal government has refused to make any portion of this agreement public, or divulge the cost, citing the need to protect commercial secrets.

Mr. Turp, for his part, said it was disappointing that it required a lawsuit to force the federal government to divulge this information.

"If you need to go to court for more transparency that's really something that is unacceptable in a democratic setting like Canada," he said.