Canadians shouldn't be concerned over the risk of a potential terrorist entering the country among the 25,000 refugees Prime Minister Justin Trudeau has vowed to resettle before the end of the year, as all of them will face a rigorous screening process, according to one expert.

Peter Showler, the former chair of Canada's Immigration and Refugee Board, says there’s a big distinction between refugees resettling in Canada and the hundreds of thousands of displaced people streaming into Europe.

"There's a vast difference between the outpouring of 700,000 refugees pouring into Europe with no security screens, and the kind of security screens that are in place for every refugee that is resettled from the Middle East," he told CTV's Canada AM.

Concerns over the refugees fleeing the civil war in Syria are ramping up, after a Syrian passport was found lying close to the body of a suicide bomber in the deadly Paris attacks. It has not been determined if the passport is authentic or a forgery.

Greek officials said the man linked to the passport entered the country through Leros in October. Leros is one of the islands used as a gateway to Europe by refugees fleeing the violence in Syria and Iraq.

The Liberal government says it is still planning to resettle 25,000 refugees in Canada before the end of the year, despite calls from the Official Opposition to adjust the timeline.

In a statement to CTV News on Monday, Immigration, Refugees and Citizenship Minister John McCallum said that "effective security screening has always been paramount" in the government's refugee resettlement plan.

"The government is committed to a rigorous, balanced and compassionate response to this humanitarian crisis," said McCallum.

"This operation will be done without compromising security," he added.

Showler said the screening of refugees, which involves three different phases, is robust.

First, the UNHCR has already triaged the refugees and assessed those that would make ideal candidates for re-settlement, he said, noting that less than five per cent of asylum seekers make that initial cut. For these candidates, there is additional security screening so that UN officials can learn their stories, he added.

Second, Canadian visa officers conduct more screening and interviews with this group to ensure there is consistency in their cases, he said.

And finally, there is an additional security review of the candidates by Canadian security agencies, including CBSA, CSIS and the RCMP.

Showler said the entire process can be fairly quick, especially with the help of officials working on the ground in refugee camps and in countries where refugees have fled to.

"If you're living or working on the ground… you actually know a lot about refugee flows," he said, noting that experts and staff working in camps will be able to generally determine which refugees pose a security risk and which don’t.

He added that, when the Syrian civil war began four years ago, the first refugee flows out of Syria were people who were primarily secular, politically active and pro-democratic.

"They've now been in the neighbouring countries as refugees for four years," he said. "We know who those people are.

"So it's actually quite easy to identify 25,000 that fit into extremely low-risk security categories."

Over the weekend, Conservative interim leader Rona Ambrose urged the Liberals to ensure that the refugees can be resettled in a "secure manner."

Also Monday, Saskatchewan Premier Brad Wall also wrote a letter to Trudeau, advising him to suspend the plan over safety concerns.

"I do believe that if there's a chance that even only one person would use the refugee process to come into this country with a plan to do ill, to do bad things in Canada to Canadians, that's worth it, that's worth some circumspection," Wall said, speaking in the province's legislature.

Wall said that the devastating terrorist attacks in Paris, which killed 129 people and injured hundreds more, demonstrated how even a small number of "malevolent individuals can inflict upon a peaceful country and its citizens."

Wall said he is concerned the security screening process could be undermined by expediting the process to bring 25,000 refugees to Canada by the end of year.

He added the government's goal shouldn't be driven by a "deadline and quotas," but should be focused on safety and effective resettlement.

With files from The Canadian Press