Workers at the screening position were later suspended amid evidence their selection of the Foreign Minister was "not random" and therefore breached airport security protocol. Julie Bishop at Canberra Airport earlier this year. Credit:Andrew Meares But mystery has surrounded what initially prompted the investigation. A spokesman for Deputy Prime Minister Warren Truss confirmed on Friday that his office had contacted Melbourne Airport to raise concern about the incident after being "informally notified" about Ms Bishop's treatment. He said: "Our office was informally notified of the incident and no action was requested or sought in relation to it.

"The DPM's [Deputy Prime Minister's] office raised the matter with the [Transport] Department and Melbourne Airport. Melbourne Airport undertook an investigation and acted accordingly." A spokesman for Warren Truss said his office had contacted Melbourne Airport to raise concern about the incident. Credit:Alex Ellinghausen The government's direct hand in the matter appears to place a question mark over an official response by the Department of Foreign Affairs and Trade. It was asked on notice in November about the incident. The question submitted by Labor Senator Catryna Bilyk asked: "Has the Foreign Minister ever been involved in any incidents, altercations or complaints relating to directions to subject herself to security screening at Australian ports, in relation to body scanners or other devices or procedures?"

DFAT responded: "No." The female worker who conducted the scan was found to have "not adhered to standard security screening procedures" but has since been reinstated after undergoing further procedural and customer service training. But the male co-worker who instructed her to screen Ms Bishop has been sacked. Melbourne Airport said in a statement: "A male ISS worker's employment was terminated as a result of not adhering to standard security screening as required at an Australian international airport." It is understood that a third worker, a woman, at the same position was also stood down as the matter was investigated.

The sacked worker initially sought advice on an unfair dismissal action, but is believed to have reached a financial settlement with the airport that may have included a confidentiality agreement, a source close to the disciplinary process said. He was covering in the screening position for a fellow worker who needed a bathroom break when he recognised the Foreign Minister, a regular VIP through the airport. During the investigation, the man was told that Ms Bishop had felt "uncomfortable" at his presence in the screening. Ms Bishop's office has turned down all requests to explain any action taken after the incident. A spokeswoman said on Friday that there was nothing to add to the minister's position outlined on Thursday. "Neither the minister nor anyone from her office has made any official complaint regarding her transit through Melbourne Airport at any time," her Thursday statement said.

But a number of airport workers who contacted Fairfax Media on Thursday and Friday said it was common knowledge that the airport had acted on a complaint from government. An airport worker said: "It was made very clear to people throughout the airport that complaints had come down from Canberra, including the Transport Department and a minister's office." Talk about the incident had done the rounds of the union movement despite the union covering ISS workers in Melbourne, United Voice, attempting to keep a lid on the matter once the female worker was reinstated. That led to Senator Bilyk submitting the supplementary question on notice as part of the October 22 Senate estimates hearing for DFAT. Follow us on Twitter