Australia began an exercise on Monday using part-time workers such as university students and retired people to screen passengers at airports, drawing criticism that the plan would endanger security.
The test run at Sydney and Adelaide airports involves 23 people checking the passports of outgoing passengers.
It was quickly criticized by the Labor opposition, which said it would weaken border security and the work of the Australian Customs service, and from trade unions who described it as "a silly attempt" to address staff shortages.
"Customs officers play an important role in passenger movement and border security, including identifying contraband being smuggled out of the country, which may include Australian wildlife," Labor's justice and customs spokesman Joe Ludwig said in a statement.
"These are not turnstile positions. This is an integral part of Customs' work."
But Justice and Customs Minister Chris Ellison rejected Labor's claims as scaremongering and said the exercise would be fully supervised.
"Any suggestion that Customs is seeking to introduce a staffing initiative that jeopardizes the integrity of Australia's border security is misleading and an insult to the organization," Ellison said in a statement.
He said the trial could provide Customs with a flexible workforce able to deal with peak periods at airports.
"This is a trial to see if perhaps it can be broadened, but it's only a trial. It's nothing more than that -- it's not a fait accompli," Ellison told Australian radio.
Australian airport security has been under the spotlight recently after a number of heavily publicized breaches.
Australian woman Schapelle Corby, who was convicted of smuggling marijuana into the Indonesian tourist island of Bali, denied the charge and blamed a lack of airport and baggage-handling security at Sydney Airport.
A Qantas baggage handler was also photographed as he drove across the Sydney Airport tarmac wearing a camel suit which he had taken out of a passenger's baggage.
