We know all about these perks and potential conflicts of interest because every politician must disclose them via Parliament's website. And, probably because of that, there are few obvious concerns listed among them. Most of the entries are trifles; the occasional upgraded flight or a corporate ticket to a sports match. Nonetheless, these disclosures still matter, because we need to know what may influence our parliamentarians' votes. It's a small part of what keeps Australia from sinking into the deep corruption in which so many other countries are mired.

But monitoring parliamentarians' interests misses a pretty big point. The federal government buys about $25 billion of goods and services a year, of which more than $10 billion worth is sourced directly (i.e. without competition). Ministers usually have nothing to do with these purchases; senior public servants decide from whom to buy and, if there's a tender, who is invited to submit a bid.

Yet what do we know about these decision makers? I can't check the companies in which these officials (or their spouses) own shares, the gifts they receive or the organisations to which they belong. Yes, the Public Service Act requires that public servants disclose and avoid conflicts of interest, but senior executives need only make such declarations privately to their agency head. As a result, the people best placed to actually discover a hidden conflict – such as those business owners who miss out on government contracts – are unable to scrutinise effectively most purchasing decisions.

Here's an example of what this means in practice. Over the past few years, a federal government agency has awarded tens of millions of dollars in contracts to a firm that's closely linked to one of its senior executives. (The executive's wife has a lead role in a company owned by the firm.) When I questioned the agency about this link, its spokesman said the executive had conducted himself with "the utmost probity and ethical standards in relation to contract procurement". Perhaps so. But the agency refused to show me the executive's declarations of interests. Instead, I was told simply to accept assurances that the official "is not and nor has he ever been involved in tender processes involving" the firm.

That may be an acceptable proxy for scrutiny in Nigeria, but it's a bizarre notion of accountability in a Western liberal democracy.

So I applied for the executive's declarations under freedom of information law. The agency knocked back my request, saying granting me access to the documents would breach the privacy rights of the people named in them. (For some reason, it overlooked the simple option of redacting the names.) The agency also told me that disclosing the declarations would "prejudice the management function of the department, noting staff may be reluctant to take up positions if conflict of interest declarations were routinely disclosed to the public".

Read that closely: the agency fears that asking senior public servants to account to the public is a step too far, and would even jeopardise government recruitment. That argument would deeply offend many of today's upstanding public service leaders.

I won't name the agency or the executive; this isn't about "shame". The point is there may be dozens, even hundreds, of similar cases here in our city, involving the expenditure of many millions of dollars of public money. We don't know how many of these conflicts of interest are disclosed internally, nor can we check.

There's a simple remedy: agencies could publish their executives' declarations of interests, as well as the names of all staff who sit on tender assessment panels. Until they do, they'll continue to invite corruption.

This article was first published in Forum on March 31, 2012.

Markus Mannheim edits The Public Sector Informant. Send encrypted tips via the Signal SMS app (+61428280114) or email psi.editor@canberratimes.com.au.