Ottawa has agreed to negotiate a bilateral extradition treaty with China – a move that took place a day before jailed Canadian missionary Kevin Garratt was ordered deported from the country.

Prime Minister Justin Trudeau's national security adviser met a high-ranking Chinese official in Beijing last Monday to hold talks on the issue, which a former Canadian dipomat suggests was a quid pro quo between the two countries for Mr. Garratt's release.

Long demanded by China, an extradition treaty would commit Canada to transfer fugitive Chinese officials to a country known for biased courts and harsh interrogation methods and where the death penalty is routinely imposed even for non-violent crimes.

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Foreign Affairs Minister Stéphane Dion and other senior officials have said Canada made no concessions for the return of Mr. Garratt, who had spent two years in a Chinese prison on trumped-up spying charges.

"It's not the style of the Prime Minister," Mr. Dion told reporters Friday in Montreal when asked if Canada had made a deal to bring Mr. Garratt home. "Prime Minister Trudeau doesn't do these kinds of things."

Former diplomat Charles Burton said it appears China used Mr. Garratt as a bargaining chip to get what it wanted, including a role in helping Canada Border Service Agency agents identify illegal Chinese immigrants.

"The Chinese government is just a very sophisticated actor with a lot of experience in dealing with Western governments and it seems we may not have been operating with the same degree of care and sophistication in our negotiations with them," said Mr. Burton, who served in Beijing.

The Liberal government never publicly mentioned that Daniel Jean, the Prime Minister's national security adviser, met over the extradition treaty on Sept. 12 with Wang Yongqing, secretary-general of the Central Political and Legal Affairs Commission of the Communist Party. The treaty would allow both Canada and China to share the financial assets that suspected Chinese fugitives have brought to Canada.

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The two men also agreed to conclude a transfer-of-offenders treaty and to finalize negotiations on a pilot project "where Chinese experts will be invited to assist in the verification of the identity of inadmissible persons from mainland China in order to facilitate their return from Canada," according to a joint communiqué posted on the website of the Prime Minister's Office.

A day after these talks were going on in Beijing, a Chinese court convicted Mr. Garratt of spying, released him on bail and ordered him to leave the country. He arrived safely in Vancouver last Thursday.

Mr. Garratt's release had been interpreted as a goodwill gesture in advance of a working visit by Premier Li Keqiang to Ottawa on Wednesday for high-level talks with Mr. Trudeau.

Conservative foreign affairs critic Peter Kent said it is "much more than a coincidence" that Mr. Garratt was deported after Canada entered into formal negotiations on an extradition treaty.

"This is the Chinese objective much more than ours obviously to get back home those they have accused of corruption and fleeing with wealth," Mr. Kent said. "Corruption is a very broad definition in China. We have seen incarceration, torture and execution on a lot of cases where we know there has not been due process."

Mr. Burton said the federal Justice Department has argued against Canada signing an extradition treaty, even if there is evidence that some of the fugitives that China is seeking are engaged in criminal activities.

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"We don't have an extradition treaty with China for fairly clear reasons. The rules of evidence are not the same there. There are reports of death sentences for white-collar crime and pervasive evidence of torture and interrogation," Mr. Burton said.

Canada usually forbids the extradition of people to countries with the death penalty, although Chinese fugitives have been repatriated on condition they are not executed and that Canadian diplomats are permitted to visit them in prison.

"Practically speaking, if we started to send back quite a number of Chinese nationals to China that we had concerns about, I don't think we really have the capacity to monitor all of them in prison," Mr. Burton said.

In 2011, Canada repatriated Lai Changxing, who was accused in China of heading a multibillion-dollar smuggling operation. China reassured Canada he would not face the death penalty.

China has also sought the return of one of its spies in Canada to avoid extradition and a lengthy prison sentence in the United States. Last year, over strong Chinese objections, Canada extradited Su Bin, who held permanent residency, to California to face charges as the ringleader of a Chinese military hacking operation.

Canada has returned more than 1,400 Chinese nationals since 2009, mainly involving illegal immigration.