Their arguments can be sweeping and carelessly naive. Countries with less perceived corruption than Australia don't have a national integrity commission, so nor should we. Never mind the fact many are smaller nations, and all carry different political systems, histories, spreads of wealth, economic bases and bureaucratic architecture. And forget that Australia has slid in rankings of perceived government integrity since 2013.

Others argue the federal government deals less in work at high risk of corruption, such as planning, making its officials less vulnerable to the scourge. Just ignore the billions of dollars in procurement happening at a Commonwealth level, and the issuing of government grants.

Momentum for a National Integrity Commission is gathering fast now that crossbenchers have won more control over the federal government's agenda since the Coalition lost its majority. They've decided to focus on setting up a new watchdog, a push that could be one of the last major reforms tabled in a year that began with a revelation that 5 per cent of Commonwealth public servants had reported witnessing corruption.

The scepticism from some quarters towards a new commission may have some problems. There are also good reasons to question the need for another integrity agency when the government already has several. Will a federal watchdog trample on the delicate jurisdictional balance achieved under the current patchwork that includes the public service commission, the commission for law enforcement integrity, the audit office, and the ombudsman?

Even the creation of an ACT anti-corruption commission, to be debated this week, has raised concerns from the commission for law enforcement integrity about overlap. Will a National Integrity Commission create more clashes?

Maybe it will. That could be a virtue, and a capacity to shake up the more complacent, opaque parts of the federal bureaucracy could be just what's in order. Corruption can exploit the orderly veneer of a bureaucracy that tries to eschew scrutiny where it can. The whole point of a National Integrity Commission would be to shatter such shields and see what's underneath.

Would a new commission overreach? It might, which is why any legislation creating it would need debate and careful design. There's no reason to throw out the idea.

Looking at the figures is helpful too. These paint a nuanced picture. The Australian Commission for Law Enforcement Integrity has reported its largest ever caseload. The public service commission reported fewer code of conduct investigations in 2016-17. Taken together, these figures could confirm or undercut the case for a National Integrity Commission, depending on how the statistics were used.

Advocates for a new anti-corruption watchdog need to explain better the kind of conduct it would investigate. What are the candidates for its first inquiry?

Trust in government, and opinions about democracy, are worsening in Australia. The problem is arguably the most serious in national public life. That is why the solutions should be well-argued and carefully designed. A failed, ineffective National Integrity Commission would only aggravate the nation's eroding faith in its democratic institutions.