The silliest aspect of the ban is Malcolm Turnbull's rationale for it: he put it in place because "the public have high expectations" of ministers' "decorum", and because ministers' "families deserve honour and respect".

Not a word was mentioned about the only good reasons for even considering such a ban, which would be to avoid conflicts of interest, nepotism or being exposed to potential blackmail. And while there was a whiff of nepotism – at least according to the opposition – in the appointment of Barnaby Joyce's former adviser Vikki Campion to the staff of other Nationals frontbenchers, there was no unlawful conduct; parliamentarians can largely hire whomever they want.

Yet that's not so in the Australian Public Service. Even in these times – when contractors and labour-hire grunts are often used in lieu of public servants, despite questions about the legality of doing so – there is the tricky matter of all government employment decisions needing to be merit-based, and all purchase decisions needing to represent best value for money.

Which is why sex is a big deal in Canberra. Not in Parliament – they can screw all they like up there, as far as the public should care – but in the bureaucracy. In fact, not just sexual relationships but other ties, too.

For all the attention paid to parliamentarians' financial interests, the gifts they receive and the company they keep, they are not the Commonwealth's corruption problem. The federal government enters into about 70,000 contracts a year, worth about $50 billion. Ministers see almost none of these, nor are they aware of most of them. This spending on our behalf is managed and approved by senior and mid-level public servants, about whom we know almost nothing.

This is the heart of Australia's real corruption risk, though few backers of a federal anti-corruption watchdog have articulated it. It's not in high-profile bribery cases (think AWB and Securency) or in foreign nationals seeking to influence parliamentarians (hi, Sam Dastyari). The risk lies in the regular work of public servants, when they choose whom to hire or contract. Small, "harmless" decisions; creeping, subliminal cronyism. Indeed, I suspect that in many cases the people making unethical spending or recruitment decisions may be unaware of the biases that are influencing them.

Almost all of this comes down to failures to manage conflicts of interest effectively, whether those conflicts are real or perceived. It hasn't helped that, until recently, there was a lack of clarity about how to approach the most common of potential conflicts: friendships (whether sexual or not). In 2014, the Auditor-General's office reported on how government agencies were managing staff conflicts of interests. In many workplaces, it was unclear whether mid-level and junior officers needed to declare them. The audit also found that agency heads' instructions to staff "usually contained very little information".

Yet since then, the Public Service Commission and the Finance Department have made their guidelines clearer. And it may be surprise some public servants, but their advice is unequivocal: if you're on a selection panel and you've slept with someone who applies for a job, promotion or contract, you need to tell your departmental secretary, or at least one of your managers. It doesn't matter whether the sex was a week ago or a decade ago.

Imagine just how messy this could become, especially in hopelessly conflicted workplaces like the Defence Department. There, it's extremely common for public servants and ADF personnel to move from working for government to working for the businesses that supply the military. Not only do public servants find themselves negotiating across the table with former colleagues, who are often good friends, but in many parts of Russell they then share the same offices; contract managers and contractors working side by side on the same project.

Consider the hypothetical case of Wendy, an EL2 officer whose section works on naval missile-guidance software with an industry partner, Very Big Guns Pty Ltd. She had a big night with a Big Gun, Warren, a few years ago at a trade expo. It was a one-off, but Warren still comes into the office regularly and they have working lunches occasionally.

The Big Guns are seeking a contract extension, and Wendy is a subject-matter expert in a very specialised field. It's not feasible for her to withdraw from the panel that will discuss the Big Guns contract; she's needed. The Public Service Commission (indeed, the law) offers no wriggle room: "where a material personal interest cannot be avoided, the employee must disclose that interest so that it can be managed".

This isn't a fanciful example. Russell is its own community, where everyone kind of knows everyone else. In fact, most government workplaces in Canberra operate in similarly small circles. We befriend (sometimes intimately) those we work with, buy from and sell to. And then, occasionally, we decide whether to award them a job or a contract. Depending on the nature of that relationship, we might improperly favour them or even be biased against them (maybe Warren's presence makes Wendy feel uncomfortable these days).

But does anyone really believe Wendy is willing to pick over the details of that night at the expo with her branch or division head? More likely, she'll keep it to herself and believe herself entirely capable of dealing with the conflict sensibly.

Yet that shouldn't be her decision. Disclosure is the new legal norm (even if no one does it). Home Affairs Department chief Mike Pezzullo told a recent Senate estimates hearing that he expects to be told (or his delegates to be told) of all office relationships that could affect his portfolio's work. "As to relationships within the workplace, we have a general policy that is applicable to everyone, from myself down – the [Border Force] commissioner down – that all such relationships are to be declared to ensure that there is no conflict of interest." So more of a bonking broadcast than a bonking ban.

The commission is still loathe to map out exactly what public servants like Wendy should do; a spokeswoman said it depended on the case.

"In general terms, the employee should disclose the relationship to a senior decision-maker and discuss what steps are required to manage the conflict. This may involve them excusing themselves from the process altogether," she said.

And who should decide whether Wendy (or whoever) should leave the panel? Again, "it depends", though the spokeswoman told the Informant that the legal onus was on the employee to stand aside "if that is the reasonable approach".

"In practice, this is likely to be discussed with a senior decision-maker and an agreed approach reached between them."

In other words, an awful lot of faith is placed in public servants, who are expected to talk about something they'd almost certainly rather no one knew. In Wendy's case, she'd especially rather her Defence colleagues not be told, as most of them know Warren. The integrity of the system relies on extraordinary individual integrity. Hmm.

There's a solution to this mess. It would help to expose a wide range of nepotism, cronyism and "green-lighting". It would cost nothing, and would be an enormous deterrent to anyone considering hiding a conflict of interest.

Simply publish the names of public servants who sit on assessment panels, whether for jobs or contracts. In a small city like Canberra, it would greatly increase the risks associated with improperly hiding a friendship. Someone might eventually spot that a public servant had "forgotten" to disclose that the person they'd recruited, or awarded that $300,000 marketing deal, was a neighbour, a mate or an in-law. It would hardly be an invasion of privacy; we already publish the names of contact officers, as well as the name of every person who joins the APS or wins a promotion.

The question is: why aren't we doing this already?

Markus Mannheim edits The Public Sector Informant. Twitter: @MarkusMannheim