Should the minister resign? Should the premier (prime minister or chief minister) sack the minister?

These questions invariably evoke the principle of ministerial responsibility.

The principle began in Westminster at the end of the 17th century. The Commons wanted to hold the Crown to account. In its purest form it holds that the minister is responsible for his or her department and if anything goes wrong, the minister should take responsibility and resign.

That is the form invariably invoked by the public, the media and the opposition whenever there is, to use a colloquial phrase, a "stuff-up". They do so because they are baying for blood. The opposition wants a scalp. The media wants a good story. The public want someone to blame.

But there are many kinds of stuff-ups with varying degrees of veniality, culpability, size, and vicarious or actual fault.

In fact, at the federal level there has never been a case of a minister resigning over a departmental failure unless the minister knew about, had a part in it, or covered it up.

To use another colloquial phrase, the principle of ministerial responsibility applies only when the minister's "fingers are all over it".

If the minister had no personal fault, they usually stay in place. A good example was Peter Garrett who had carriage of the Home Insulation Scheme in the Rudd government. The scheme resulted in the death of four insulation installers and massive fraud and waste. He did not resign, nor was he sacked, despite calls by the opposition and the media for him to go because no-one could show any personal fault.

Of the 119 federal ministerial resignations since federation, half were over disagreements with the prime minister or policy disagreements and the other half were over personal malfeasance, such as conflicts of interest and travel rorting.

The thinking behind the original Westminster principle of ministerial responsibility was that the minister was responsible for whatever his or her department did because the minister employed them and should have systems in place to ensure they behave competently and honestly.

Moreover, public servants should be shielded from public scrutiny. They could take no credit for success or blame for failure. That was for the minister.

But that principle, is not just dead. In Australia it was never alive.

As then-prime minister John Howard correctly said in 2001, "It's never been the ministerial principle that you resign if something goes wrong in your department."

Howard's ministers dropped like flies early in his prime ministership because of conflicts of interest. Or more correctly because of the unduly strict definition Howard gave to the term in his edicts on ministerial conduct, which he later went back on.

The 2020 standards of Ministerial Ethics published by the Department of Prime Minister and Cabinet in 2010 lay out the ministerial standards, but make no mention of resignation or sacking if they are breached.

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Strict ministerial responsibility was just a figment of the imaginations of oppositions, the media and the public. It should not be a principle for several reasons.

Modern, large government would become unworkable if ministers had to resign over departmental failures in which they had no part or could not reasonably have been expected to have a part.

For the past half century many new avenues of accountability have opened: freedom of information, parliamentary committees, inquiries of various levels, and anti-corruption bodies, for example.

Often accused ministers will resort to any or all of these (bar freedom of information) to delay or avoid resignation and the leader will do the same. This is happening with Ayres now, as the Upper House continues its inquiry into the Barilaro case and Premier Dominic Perrottet's own hand-picked independent inquirer former public service commissioner Graeme Head continues to inquire.

Ultimately, though, the principle of ministerial responsibility boils down to: "Never act in a way that embarrasses the government or the leader to the extent that they are better off wearing the opprobrium of a lost scalp than the continued presence of the embarrassment".

The bigger the failure and the more victims it has, the more that principle applies.

This, of course, is subject to another principle: "A leader should always balance the risk that a ministerial sacking might be cleansing but it could also result in an unwanted byelection."

This was well-illustrated in 1994. When Labor's Ros Kelly resigned over the sports rorts affair (Version 1) in 1994. She left parliament and the Liberal Party won the hitherto safe Labor seat.

Perrottet has this difficulty now. He is in minority with 45 seats and relying on the crossbench. He has a lot of other troubles. He would like to get this over with painlessly. The principle of ministerial responsibility, if it exists, will not help him.

Ayres has his fingers all over this failure. A political crony (former deputy premier no less) has got a plumb job in New York which the minister had a hand in creating and selecting the candidate. The victim is the person originally selected, but lost her job.

But countering is the fact that Ayres holds the very marginal seat of Penrith. He got just 51.3 per cent of the two-party preferred vote last election. A byelection would be near fatal for Perrottet's minority government.

These considerations will play a much more important role in Ayres's fate than ministerial responsibility.

Of course, it would not be possible for the Premier to promise Ayres a plum job if he would just quietly fall on his sword.

Nearly all the time, politics is much more an art than a science or a set of principles.

That said, we are seeing calls for more accountability, at least in the federal sphere. But expect it to be more about personal standards of ministers and their dealing with public money than an esoteric principle of ministers taking responsibility for whatever happens in their departments.

The Ayres-Barilaro case is all about personal standards and ethics, not ministerial responsibility.