Political careers can unravel in not much more than the metaphorical blinking of an eye. Often, only astute management stands between a parliamentarian surviving a serious allegation or tumbling into oblivion.

On that basis, Darren Hughes, one of Labour's most promising MPs, has been ill-served by his party's leadership. When he stood down yesterday as Labour's education spokesman and chief whip, it served only to underline the folly of Phil Goff's mishandling of the incident.

Quite reasonably, Mr Hughes' case is being compared with that of Richard Worth two years ago. At that time, the Labour leader was adamant the Prime Minister should have immediately sacked Dr Worth after being told of allegations, also of a sexual nature, against the then National minister.

John Key's indecisiveness then provided ammunition for Labour and led to an inevitable snowballing of matters. Yet Mr Goff seems not only to have failed to learn from that episode but to have decided to apply a different standard to Mr Hughes.

He was told of the allegations against the MP two weeks ago, and took no action. Presumably, he hoped it would not become public knowledge and would simply go away.

That was never going to happen, given the questioning involved in the police investigation into the complaint by an 18-year-old male student. The only viable option for the Labour leader was to go on the front foot and immediately stand Mr Hughes down until the inquiry was completed.

Yet even when the incident was publicised, he still tried to sidestep it by placing the MP on leave until the investigation was completed. Only if the police found there was substance to the complaint would he "need to act accordingly".

Yesterday, in attempting to explain why he had not acted at once, Mr Goff suggested his harassment of Dr Worth had been wrong. People were entitled to be regarded as innocent until proven guilty, he said. There is an air of wanting to have it all ways in this.

How can it tally to suggest, in the first instance, that the subject of an allegation can carry on as normal until substance to a complaint is found, and yet then strip an MP of his responsibilities?

The action against Mr Hughes yesterday finally saw Mr Goff resorting belatedly to the prevailing political orthodoxy. There are good reasons for this approach.

It demonstrates a decisiveness that plays well to the public. It also signifies a recognition that incidents such as this will not simply fade away, and that political parties cannot get away with saying and doing nothing.

Mr Hughes' alleged behaviour raises issues of clear public interest. In the lead-up to the complaint, he had been representing the Labour Party in a debate at Victoria University.

Then, even if charges are not laid, there is the issue of age and what it says about the MP's judgment. He is 32, the complainant is 18.

It is highly debatable that Mr Hughes' political career can survive this controversy, whether or not the police decide to prosecute. Dr Worth first resigned his portfolios and then quit Parliament even though no charges were laid.

The Prime Minister decided his ministers should have standards of behaviour higher than those defined by criminal law. As much as parliamentarians may rail against this, that is now a fact of life.

Mr Hughes can hardly have failed to know this, or that politics can be a tenuous occupation. After all, only last week, as part of the winning team in a press gallery fundraising debate, he affirmed "that politics is a grubby business".

Now he also knows unpleasantness can escalate especially rapidly when muddled management is thrown into the mix.