Independent senator Nick Xenophon.

''My senior officer and the rest of the unit was absolutely dumbfounded'' … Allan Kessing on Friday, with Senator Nick Xenophon in the background. Photo: Peter Rae

WHEN explosive allegations were made this week that corrupt customs officers had been accused of smuggling drugs through Sydney Airport, Allan Kessing sat back and thought: It's about time.

The former customs officer had been trying to tell authorities for the past decade of what he described as the ''shocking'' security situation within the airport and security lapses among its staff.

He knew, he says, because he was the man charged with investigating them.

In 2002 and 2003, when Mr Kessing was working in the covert Air Border Security Unit within customs, he was asked by his senior officers to compile a report on the potential for corruption and systemic issues of security within customs.

What he uncovered at the airport was disturbing, he said on Friday. Up to 20 per cent of those people he investigated with an airport security clearance had criminal convictions, he said.

Some were illegally in Australia, and yet were policing people entering and leaving the country. At least two were absolutely undocumented - without a driver's licence or passport or any proof of identity.

But more shocking was that his two comprehensive reports into the situation were completely ignored, and the information within them was suppressed.

''My senior officer and the rest of the unit was absolutely dumbfounded and [we] asked for a sit-down with the airport manager to explain why the obvious evidence of corruption, criminal conduct, breaches of security and real worries about infiltration by terrorists were being not only ignored, but actively suppressed,'' Mr Kessing said.

He claims the manager of airport security for customs at the time rejected his findings for being financially and ''commercially too onerous'' on the airport, Qantas and other major airport operators.

The independent senator Nick Xenophon said Mr Kessing ''deserved a medal'' for writing the reports and speaking publicly about their findings on Friday, which he did at the risk of prosecution.

In 2007, Mr Kessing was convicted for breaching Section 70 of the Crimes Act after information from his two reports was published in The Australian newspaper. Mr Kessing has denied leaking the information.

Mr Kessing said that in April 2005 he approached Anthony Albanese, then the opposition transport spokesman, and briefed one of his staffers about his concerns surrounding the reports, before meeting Mr Albanese. No action was ever taken by Mr Albanese, he said.

Instead Mr Kessing said he was the subject of a witch hunt. His home and that of his recently deceased mother had been raided in 2005, and the Australian Federal Police spent $250,000 tapping his phones and putting him under surveillance, he said.

Senator Xenophon said after this week's allegations of corruption and criminal activity at the airport, Mr Kessing should be pardoned and his reports released.