The Senate Transport Committee heard that as many as 20 per cent of airport staff with security clearances held criminal convictions for offences as serious as drug trafficking and assault.

These staff, typically subcontractors for private companies, operated behind the customs barrier and had access to passengers' luggage, the inside of aircraft and other secure areas.

In the report, Senator Nick Xenophon highlighted a number of "unacceptable" shortcomings in airport security.

"The evidence provided to the committee...showed significant problems in relation to the aviation security identity card and visitor identity card vetting process," he said.

"Up to 20 per cent of all non-Customs staff with access to the sterile areas have criminal convictions, and about half of those were serious convictions, including drug trafficking, assault and other misdemeanours."

The report highlighted the need for background checks when issuing subcontractors such as cleaners and guards with security clearance.

"Numerous aviation reviews have identified long-term and ongoing issues with the engagement, training and background checking of security screening and other airport staff," read the report.

"Despite these reviews and recommendations, some airport staffing practices continue to present ongoing and significant security risks.

"It is clear that security screening standards should remain consistent across the sector, irrespective of whether staff are directly employed by screening providers, or contracted and subcontracted by security companies," it continued.

Retired Customs officer Allan Kessing told the inquiry that these employees posed the single greatest threat to airport security, and needed to be scrutinised with "rigorous background checks".

"The greatest vulnerability in an airport is ground staff," he said.

"The majority of personnel are low-skilled, casual and part-time, yet many have access to restricted, high security areas."

Applicants for an ASIC clearance undergo a criminal record check and other vetting, however the inquiry found that current arrangements were insufficient.

For example, any convictions registered after an employee received security clearance were not automatically recorded.

"The committee upholds the view that the current self-reporting arrangements for ASIC holders convicted of an offence is not satisfactory, and raises significant security risks," read the report, released last Friday.

There are currently at least 44 bodies with the power to issue aviation security identity cards, with little overlap in screening policies and procedures.

"The committee urges the Australian Government to consider the feasibility of establishing a centralised issuing authority. Such an approach would likely lead to improved security outcomes," the inquiry found.

The Australian Airports Association is an industry body which represents 26 of the country's largest airports, including Canberra, Melbourne, Sydney and Brisbane.

In a submission to the inquiry, the association said it was working with the Department of Infrastructure and Regional Development on a number of initiatives to improve airport security.

"These initiatives have included...exploring options to improve the scope of the Aviation Security Identity Card scheme," the association said.