Self-service technology used by travellers to pass through immigration at Australian airports is unreliable and impersonators can easily cheat the system, an expert warns.

One million passengers have now used the bio-metric SmartGate self-process Customs system at airports in Adelaide, Brisbane, Cairns, Melbourne, Perth and Sydney.

SmartGate takes a photo of a traveller's face and, using facial recognition technology, matches it with the digitised image stored in their ePassport

Minister for Home Affairs Brendan O'Connor says the system has made processing through passport control simpler and more convenient for travellers.

"The popularity of SmartGate is really encouraging and we expect usage figures to continue to increase as more travellers take advantage of the self-processing option," he said.

"In the last three months alone, more than 330,000 travellers have used SmartGate at airports across Australia."

But visiting fellow at Australian National University, Roger Clarke, says the SmartGate system has "been a problem from the very beginning".

He says the technology is unreliable and unsafe.

"What it originally claimed to do for us was to be a counter-terrorism measure," he said.

"It was meant to provide greater security, greater confidence that the person who was presenting a passport was the person to whom it was issued and whose photograph appeared in it.

"[Customs] endeavoured to run some trials as to the quality of the technology ... and from everything that we can find out publicly, it performed extremely badly.

"It's quite unreliable. It's not a security measure at all."

Mr Clarke says the system has a very high tolerance, to allow people to get through easily.

"By setting the tolerance so high, anyone who is cheating the system has a very good chance of getting through if they look even vaguely like the person whose passport is being used," he said.

Mr Clarke says during tests of the SmartGate system, a large group of people swapped passports and successfully made it through checks.

"Eight out of 100 were incorrectly permitted through. That's a huge number of people, so the security aspects are dreadful," he said.

He says air crew make up most of the 1 million travellers who have used the system.

"I've been through Sydney Airport twice since they switched [SmartGate] on for the general public, and on both occasions there have been attempts by Customs officers to attract people into those queues," he said.

"Nobody understood it, nobody wanted to go, and the machines were standing there idly while the rest of us were all standing in normal queues."

A 'trojan horse'

Mr Clarke says he thinks the program is a "trojan horse".

"We think that they have really implemented this system so that in a few years' time, when they have got it installed and everybody is forced to use it ... then they'll admit it doesn't actually work," he said.

He says the Government will then enforce a new bio-metrics system that requires fingerprints.

"Everybody will suddenly be required to prove who they are through their fingerprints and let the Government own a copy of their fingerprints, just to cross borders," he said.

"That's what we think the real game plan is, because the people who are inside Customs and inside the various security and intelligence agencies are well aware that [SmartGate] is a highly deficient technology."

SmartGate was kicked off in 2005 by then-foreign minister Alexander Downer, and initially went live in Brisbane airport in August 2007.

The next phase of the program will involve the implementation of SmartGate at the Gold Coast International Airport in March.