Tipping off selected journalists in advance of a big operation is a key part of the AFP's modus operandi. It is by no means clear, yet, that the media leaks do not have AFP fingerprints all over it. Both the AFP Commissioner, Andrew Colvin, and the AFP national media office rejected two clear invitations from me on Thursday night to publicly deny any AFP involvement in the leaks.

The media office responded that because the "unauthorised disclosure" was under investigation, the AFP would make no further comment on the matter. (It is also a part of the AFP's media modus operandi to claim that operational or sub judice considerations prevent it from discussing anything damaging to the force's image. Such considerations never inhibit the AFP if it expects good publicity from trusted journalists.)

Colvin also said he noted that AFP success depended on public confidence in the force and its leaders. Commentary and innuendo this week had impugned the force's independence and the ability of its members to carry out their work objectively and without political interference, he said.

The AFP "undertakes its activities without fear or favour. The AFP rejects in the strongest terms any suggestion to the contrary. The AFP makes all its operational decisions independently, based on experience, operational priorities and the law. The AFP's primary obligations are to ensure the safety and security of the Australian community and enforce the rule of law. The AFP prides itself on its independence and integrity, and has a proven track record of these values while operating under the remit of eight individual prime ministers and their governments since it was founded in 1979."

Colvin seemed rather sensitive given that the Labor Party, which, with the AWU, was the intended target of the AFP raids, went out of its way to avoid criticising the AFP and to avoid suggesting that it was behaving, as it normally does, as a lapdog of the government of the day. Labor had Michaelia Cash and Malcolm Turnbull in its sights, and had no desire to start an unnecessary brushfire with the AFP. So instead of reproaches for the over-the-top way in which the AFP responded to the call for help from the Registered Organisations Commission, ALP statements gave ritual praise to AFP integrity, suggesting darkly that the operation was compromised by the malign acts of a minister's office.

Experienced ALP operators do not believe that for a second. Labor has not been so long out of power that it forgets how assiduously the AFP serves ministers and their political needs. The AFP behaves like a government department, not as an independent entity. Mutual dependence is fostered by close scrutiny of budgets and priorities, by regular briefings of ministers in the AFP feeding chain, and by a studied reluctance of senior police officers to investigate any matter likely to embarrass the government of the day, or, if embarrassed into a token investigation, to take it to any sort of conclusion.

Nor did many journalists hint at AFP involvement. That may damage the supply of golden eggs.

In the 38 years since the AFP was founded, I can think of only one task it took up that caused any problems or embarrassment to government. That was the investigation and prosecution of Liberal renegade and (Labor-appointed) speaker Peter Slipper for alleged rorts of travel expenses. No doubt the investigation was exhaustive and completely professional; it failed, however, to result in a conviction. By the time Slipper was investigated and prosecuted, he was, in any event, a liability to the Gillard government, and it is unlikely that anyone would have regarded the AFP as being particularly treacherous in pursuing loud public allegations being made about him.

Meanwhile, intense AFP investigations into leaks by ministers, staffers, into allegations of bribery and corruption by mates of ministers in the Australian Wheat Board or referrals of matters to the AFP by oppositions (of whatever stripe) have failed to excite any AFP enthusiasm, or forensic success. In many cases, diligent officers trying to do their duty are frustrated by the obvious antipathy of senior officers to particular investigations.

I wrote several months ago about how AFP national media briefed selected journalists in advance about raids on people accused of involvement in an elaborate tax conspiracy. Journalists were briefed in advance about the raids but also, in detail, on the alleged involvement of particular individuals, including a senior tax officer. The "guidance" went well beyond the material later presented in brief statements of fact tendered in court. Remarkably, similar "investigative journalism" by those reporters regarded by AFP media operatives as sound and trustworthy followed for several days, with any "help" from the AFP not credited.

Those not so regarded, or out of favour for failing to regurgitate AFP spin, had to be content with bland general media statements and a considerably less-detailed media conference, during which senior AFP officers basked in the limelight and assumed most of the credit for the investigation's successful outcome.

The primary effect was to poison the well and cause what, in different circumstances, police pretend to deplore: trial by media with undisclosed police aid. This is, no doubt, only an "accidental" by-product of praiseworthy efforts by marketeers to bring credit to the force.

(Five months ago, I put in a freedom of information request for AFP documents handed to these trusted journalists. I am no further advanced than the day I put it in. It is now before the Information Commissioner to consider whether, as police contend, there is any public interest in disclosure, warranting waiver of charges. One can confidently expect further lengthy delays as the AFP resists any disclosure, word by word if necessary.)

Although senior police media advisers have long exercised significant independent power within the AFP decision-making structure, one can be sure that most of the leaks coming from the media office are authorised from above. Or, at least, that more senior officers are well aware of both the strategy and tactics involved.

The beauty of it is that those on the drip will not blow the whistle on how well they are nourished. The sillier such journalists believe they are under some duty of confidence to their snouts. The more astute recognise that the AFP, like most state police forces, is a reward-and-punishment organisation, and that those who do not dance to the master get cut off. It sometimes happens that the grief is not visited on the employing media organisation as such (at least if its profile – a matter closely studied by AFP media strategists – is what is wanted.) Instead, another journalist from the same organisation is selected, groomed and becomes the recipient for information that, when published, promotes that career instead of the person who fell out of favour.

The mutual interdependence of reporters focusing on crime and police has long been a bad feature of Australian journalism. It has often been remarked that the closer the relationships, the less likely that such journalists will notice anything wrong about the way their mates and confidants act. Thus, for example, during the 1960s, the fabled good-old-boy police reporters made personalities and heroes, not villains, of police officers we now know to have been totally corrupt, such as Freddy Krahe and Ray Kelly, and others of variable honesty, such as Roger Rogerson. Their activities were exposed by outsider reporters, a remarkable number of whom were women, often in those days excluded from the blokey, boozy mutual back-slapping club.

Almost all exposure of systemic police corruption and incompetence demonstrated by royal commissions in the states (if never at federal or territory level, because such inquiries have been avoided) have followed journalistic exposure, but from outside the police media club.

I have known AFP commissioners in the past to directly offer editors regular diets of inside stories in exchange for more "helpful and friendly" coverage. A good many editors do not need the message explicitly, given they are well aware of the importance of crime news, and of the many minor and major disadvantages of being out of the loop.

But more than the club is involved. Cops and commissioners in Australia enjoy a good deal of statutory discretion and independence from politicians. But the modern tendency – at federal, state and territory level – is for the police organisation to be keen to keep their own ministers well informed about police activities. Ministers do not know how to detach themselves; many commissioners are so keen to please that their very readiness to stand alongside ministers invites questions about their real independence.

The political relationship involves assiduous attention to the "heads-up" and "no-surprises" understandings, by which ministers are told well in advance of any proposed police activity likely to cause significant public comment, political embarrassment for the government, or when there is some "opportunity" for a minister to look good. Ministers like to look good. The satisfaction of that appetite also gives publicity-hungry senior police bureaucrats, up to commissioner level, occasions to look thoughtful and wise, alongside ministers, prime ministers and, these days, Australian flags.

Keeping the minister informed involves keeping his or her office informed. If a minister, or ministerial adviser, sees a political opportunity in leaking something, police are at a deniable distance. All the more so if one staffer tips off a staffer in another office.

Police involved in such matters are not politically naive. Many ambitious cops recognise the advantage (once regarded as a handicap) of doing a stint as a liaison officer in their minister's office. Some such liaison officers have, in the past, become great favourites of ministers. Some years ago, a minister became angry that one such favourite did not get a promotion and, in effect, went on strike, for over a month, refusing to process any AFP paper at all. The commissioner got the message.

This week saw selected journalists tipped off about AFP raids on the AWU. Labor spokesmen accused ministers, or their staff, of tipping off media. This suggestion was made before question time on Wednesday and Cash, and her senior media adviser, David De Garis, attended on Turnbull to brief him before question time. Turnbull was told, apparently, that Cash was not the source of any leaking. Either Turnbull did not think to ask a follow-up question – whether Cash's office was involved – or he did and was lied to. During the afternoon, Cash indignantly and repeatedly denied that either she or her office had tipped off the media.

Journalists who were on the drip stayed mum. Or at least some did (and some of these believe that those who admitted getting a tip-off were unethical in betraying the source of their story, which is rubbish). But two unnamed journalists told a reporter from BuzzFeed that De Garis had tipped them off. After this went online, De Garis resigned and Cash, still insisting she had no advance information, corrected the record.

Cash said De Garis himself was tipped off by a media source. But she has rebuffed efforts to get further and better particulars, and has shown a studied uninterest in having the matter, and the apparent total disloyalty to her, investigated.

A pity, unless there are still facts undisclosed that would compound her existing problems. Until the truth emerges, the media, and the public, are likely to focus on her inept management of the affair, not the original point of the exercise, which was the hope of putting an unfavourable spotlight on Bill Shorten.

It is, of course, entirely possible that the ultimate source of De Garis's information was an over-responsive public servant in the Registered Organisations Commission, though even the possibility of this seemed to have been ruled out by its commissioner, whose own management of the matter has itself been criticised.

My bet, though, is that the ultimate source of the leak was the AFP. While that is a live and obvious possibility, it is entirely wrong for the AFP to investigate the leak.

Not that there is any risk of the wrong person being charged. The successful investigation of leaks has never been an AFP speciality. I can think of only one leaker, a young Aboriginal public servant, ever found by detective work.

How well do I recall the remark of a senior AFP officer, commenting when ministers pretended to want an inquiry into the source of a leak of a classified document from Alexander Downer's office to ideological soulmate Andrew Bolt. He remarked that the detectives who couldn't solve that one wouldn't be able to find their bums with both hands.

Alas, despite this public encouragement, a no doubt very diligent investigation was unable to bring any miscreants to justice. Derrieres remain covered up.

Jack Waterford is a former editor of The Canberra Times. jwaterfordcanberra@gmail.com