If defence officials suspected that Fitzgibbon's friendship with Liu involved a security risk, they should have referred it to ASIO. A few years ago, complaints about the security implications of a relationship between another defence minister and an Asian woman were flicked from defence to ASIO, which found them to be baseless.

It is extremely unlikely that the chief of the Australian Defence Force Angus Huston, or the departmental head Rick Warner, authorised any investigation of Fitzgibbon. But Fitzgibbon appeared to see the alleged investigation as retaliation for his efforts to shake up defence.

The more likely explanation is that any snooping was authorised on a highly secretive basis by a senior official with a personal suspicion about a link to Chinese espionage. But ASIO, which has the expertise in this area, announced last Friday that it had nothing on Liu “which would have given rise to any security concern regarding her activities or associations".

The Opposition Leader Malcolm Turnbull initially demanded that Fitzgibbon be sacked because of a "complete breakdown" in relations with his department. Whatever other problems exist, Fitzgibbon can hardly be blamed if defence officials snoop around his personal computer files in violation of safeguards designed to protect Australian citizens. Turnbull was on firmer ground in arguing that Fitzgibbon should be sacked for misleading parliament because he failed to declare on his pecuniary interest statement that Liu had funded trips he made to China in 2002 and 2005.

Turnbull was also right to ask the Inspector General of Intelligence and Security (IGIS), rather than the defence department, to investigate the claims about defence officials hacking into Fitzgibbon's computer. The head of IGIS Ian Carnell subsequently decided to do so. Although it is no longer acceptable for police to investigate police, Rudd, however, was happy to leave the defence department to investigate itself in this case.

Even though the departmental inquiry had barely begun, Warner announced last Friday that no evidence of wrong doing had been found. But Warner hardly boosted public confidence in the outcome by asking the Defence Security Authority to conduct the internal inquiry. This decision was taken despite the possibility that some DSA security officials may have been involved in the alleged intrusion into Fitzgibbon’s personal files. Perhaps attitudes have changed, but defence's security apparatus previously included a body called OSCAR (the Office of Social Clearances and Research), which was regarded by some insiders as over- eager to act on the flimsiest suspicions against senior military and civilian officials.

Rudd is not keen on outside investigations when behaviour problems arise in defence or the Australian Federal Police. He is content, for example, to have an internal inquiry into a recent operation in which Australian troops killed five Afghan children by throwing grenades into their houses, apparently in the mistaken belief that this would kill members of the Taliban. What is really needed if an independent inquiry into what happened and whether the risk of killing innocent civilians — and helping the Talban's recruiting effort — is too high in these sorts of operations.

After a limited inquiry made adverse findings about the AFP's appalling conduct in pursuing an innocent doctor Mohammad Haneef, Rudd insisted he still had full confidence in the commissioner Mick Keelty. This time, if the allegations stand up, heads must roll.