Terrorists could be among the 12,000 Syrian refugees Australia is set to resettle, and Cabinet should seriously consider cancelling the intake, according to Government senator Cory Bernardi.

"We have extremist elements at work in this country," Senator Bernardi said during an interview on ABC News 24's Capital Hill.

"Why would we risk bringing in more to add to their ranks, even potentially, and bear the financial and social burden that comes with that?"

The first five refugees arrived in Perth last week after being processed by the United Nations.

Senator Bernardi said proving the back story of those being selected by the UNHCR was near impossible, and the Government needed to reconsider its decision.

"In our previous refugee intake, we've had examples where people who've been accepted as refugees have gone on to commit terrorist acts or plan terror attacks in this country," he said.

"Now why do we think that suddenly this is going to be any different?

"There is a plethora of fraudulent and falsified documents and you can't exactly go into Syria to prove up the backstory.

"And in the absence of being able to determine who comes to this country and prove their back story effectively, I think we've got to put a stop to it."

Senator Bernardi said he initially supported the Government's decision because it was targeted at persecuted minorities.

But he said Christians were avoiding UNHCR refugee camps because they feared being attacked by Muslims.

Questions have been raised about Syrian migrants entering Western nations following the Paris terrorist attacks, with a Syrian passport found near the body of one of the Stade de France suicide bombers.

But Treasurer Scott Morrison has defended the screening in place for the Syrian refugee intake.

"These would be arguably the most pre-cleared group of people to come to Australia," he told Macquarie Media.

"These groups will obviously have a very high of review attached to it, as you would expect.

"Across the rest of the hundreds of thousands, indeed millions of people who come to Australia every year, these would have to be arguably the most screened group of people you could think of."

Justice Minister Michael Keenan said a comprehensive process was in place to minimise the security threat.

"Taking 12,000 people from Syria was the right thing to do several months ago and it's still the right thing to do today," Mr Keenan said.

"In that 12,000 cohort we're doing everything we can to give an appropriate and proper risk assessment and make sure that nobody who is coming in would be of a security concern to our country."