The Canadian military plans to open up one of its principal bases to help a major defence contractor validate design changes and quality assurance on light armoured vehicles destined for Saudi Arabia, CBC News has learned.

National Defence quietly agreed to the plan last year and signed a provision of service agreement, according to documents obtained under Access to Information legislation.

In January, the country's top military commander, Gen. Jonathan Vance, signed an additional document — known as a tasking order — which put the wheels in motion for the trials and evaluation, which is supposed to take place at Canadian Forces Base Wainwright in Alberta.

At least one opposition party and an outspoken critic of the sale say the Liberal government has crossed a threshold, going from passive to active support of the sale.

The engineering validations are being conducted on the mammoth LAV VI, an updated and more lethal version of the LAV III, which was the Canadian Army's principal fighting vehicle during the Afghan war.

The tests, which are to be conducted by the manufacturer General Dynamics Land Systems Canada at its own expense, have yet to take place, according to a government official familiar with the file.

They had been expected to happen earlier this year, but were postponed, said the source, who was not authorized to speak on the record.

A spokesman for General Dynamics would only say the company is carrying out "routine product testing" for its customers and there will be no cost to Canadian taxpayers.

"We do not comment on specific schedules or programs," said Doug Wilson-Hodge, the company's manager of corporate affairs in an email.

Cannot cancel deal

The service agreement is slated to expire at the end of year, but documents quietly tabled in the Senate last summer show defence officials are expected to begin negotiating the next phase sometime this fall.

National Defence would not comment on the arrangement other than to say the army "can and does grant access to bases and training areas, and provided administrative/logistics support" for contractors under agreements that provide for "full cost recovery."

Officials at International Trade requested the army help the company, the documents say.

The Liberal government has insisted it cannot cancel the $15-billion sale to Saudi Arabia, despite the country's human rights record and growing concern about the kingdom's war against Houthi rebels in neighbouring Yemen.

Foreign Affairs Minister defends the government's decision to go ahead with the sale of light armoured vehicles to Saudi Arabia. 2:01

But critics charge that by allowing the engineering tests to take place on a Canadian base, the Liberals have gone from reluctantly rubber-stamping a deal brokered by the Conservatives to actively facilitating its completion.

"Why is the Canadian government involved in the first place?" asked Peggy Mason, head of the Rideau Institute, a non-profit foreign policy advocacy group.

"It's troubling that the Canadian government is inserting itself so directly and is facilitating so directly an arms deal that runs directly contrary to Canadian arms export regulations, and runs directly contrary to the very strong view of the majority of Canadians who don't want Canada complicit in serious human rights abuses abroad through our sale of military equipment to countries denounced as among the worst of the worst human rights abusers."

Foreign Affairs Minister Stéphane Dion and International Trade Minister Chrystia Freeland have at various times raised the prospect of cancellation penalties, lost jobs and damage to the country's business reputation if the deal were to be sidelined.

"We'll review the process by which these contracts are assessed in the future," Dion told CBC's Power & Politics last January. "But what is done is done and the contract is not something we'll revisit."

NDP demands test be cancelled

But NDP foreign affairs critic Hélène Laverdière says the narrative that the government cannot revisit or undo the deal is slowly unravelling.

She pointed to Dion's signing of export permits last spring, a formality that allowed the deal to proceed.

"He gave the go-ahead. He gave the green light," Laverdière said. "So, you cannot and the government cannot put the blame on the Conservative government. The Conservatives started it and the Liberals just continue basically the same policy."

The engineering tests should not be allowed to proceed on Canadian government property and there should be a suspension of the agreement that allows for a proper assessment, she added.

It is not the first time National Defence has been involved in the controversial sale.

In response to a question posed before a Senate committee last year, the department acknowledged it had signed a deal with General Dynamics Land Systems to support testing of the LAV VI prototype in the kingdom's capital of Riyadh in 2011. One soldier took part in a demonstration of the vehicle's capabilities as part of the sales pitch.