A leading transport union has slammed security measures at the nation's airports saying a high turnover of staff means workers without security clearance are being granted access to high-risk areas.

The Transport Workers Union on Tuesday also raised concerns over a lack of passenger and freight screening at regional airports, saying “appropriate” security needs to be in place Australia-wide.

TWU national secretary Tony Sheldon was speaking days after authorities thwarted an alleged Sydney-based terror plot to blow up an aircraft.

“What happens at the moment in our airports is a crime,” Mr Sheldon told reporters in Sydney.

“Turnover employees are not security checked; they don’t have ASIO checks, they don’t have police checks and they’re going airside right next to the refuelling of our jets and aeroplanes flying out of this country and around Australia.”

Mr Sheldon also says casual employees working as baggage handlers, ground crew, security guards and catering staff are allowed behind the scenes without adequate training.

He is calling for a single authority to be put in charge of national airport safety.

“The eyes and ears of tens of thousands of people that work in our airports could be employed if they were properly trained,” the union boss said.

The country’s pilots expressed similar concerns earlier on Tuesday.

The Australian Federation of Air Pilots said security checks on ground staff, including baggage handlers, caterers, contractors and engineers, were too relaxed at some capital city airports.

AFAP safety and technical officer Marcus Diamond told the ABC that ground crew should be treated the same as flight crew and passengers, who are subject to strict security screening.

By Hannah Higgins