OPINION: Early this week Winston Peters playfully jabbed at my hand and suggested the police would soon be paying me a visit.

It was clearly a joke, and one that even made some sense in the context: I was asking about a referral to the police he has supposedly made over a series of media stories. For all of Peters' bluster, he's too canny to try and mess with police independence.

It's also what everyone in the beltway would call typical Winston. Behaviour that dances on the line of acceptability and would probably not be kosher if a politician with less charisma tried it. But Peters can almost always smile, say "thankyouverymuch", and stroll off happily.

ROBERT KITCHIN/STUFF Prime Minister Jacinda Ardern and the Green Party need to grow a spine and stand up to Winston Peters.

However, there's a difference between leeway for jokes and leeway for seriously unbecoming behaviour. And the prime minister has slipped this week from the usual kind of space people give Winston to be Winston into plain supplicancy.

Jacinda Ardern is yet to say anything at all about the fact the Electoral Commission made absolutely clear on Monday that the way NZ First was treating donations to its foundations was wrong.

To recap: Stuff and RNZ have revealed that hundreds of thousands of dollars have been donated to the NZ First Foundation in recent years, rather than the party. This in itself isn't the end of the world, but the money appears to have been used for political activities such as renting headquarters and graphic design, and the donations not declared to the Electoral Commission, despite many of them meeting the threshold.

This was all just reporting until Monday, when the commission issued a statement making clear that it believed some level of these donations should have been declared, and referred the matter to the police, who immediately referred it to the Serious Fraud Office (SFO).

Instead of properly taking this on, Ardern has hidden, as politicians often do, behind the perceived inappropriateness of commenting while some process is still active.

ROBERT KITCHIN/STUFF The Green Party, and co-leader James Shaw, have also decided not to properly address the matter.

Sometimes this waiting game is both useful and sensible – politicians shouldn't talk too much about murder trials before they finish.

But in this case it makes no sense. Ardern has repeatedly told media that she won't comment on the NZ First Foundation case because the SFO still had to decide to investigate it, and she didn't want to "pre-empt" it.

This would wash if Ardern was about to say that NZ First was criminally liable. It's true that the Electoral Commission did not say that in its statement, although it did make clear that it in fact can't say something like that without more investigatory powers, hence the referral to the police.

But there are ways of commenting on things without alleging criminal conduct. It is the lifeblood of adversarial politics.

Following the Electoral Commission's finding, Ardern would have been totally within her rights to say, at the very least, that she thought these donations should have been declared to the commission. She could have said she was disappointed that a coalition partner appeared not to have been as fulsome as it could have been with informing the authorities – all without alleging any kind of crime. Trying to hide your donations, even legally, is a political act that politicians should be happy to talk about.

This silence got even louder on Thursday when it became clear that NZ First had some kind of involvement in two covertly taken photographs of journalists reporting on the Foundation story, which found their way onto a right-wing blog. Peters told Magic Talk on Tuesday that "we took the photographs just to prove that's the behaviour going on", but later backtracked to say a supporter just happened to see the journalists and thought he or she should snap a photo.

Because of this shifting story, there is a muddle over exactly how involved NZ First and Peters are, a muddle that would best be sorted out by Ardern demanding a fuller explanation from Peters. Any level of involvement in this kind of tactic – clearly designed to intimidate journalists – is worth condemning, and you can bet that, if Ardern was in Opposition, she would manage it.

Instead she's not commenting, saying it is a "matter for NZ First", while her office notes that she speaks about ministerial decisions and comments, not about things said as party leader.

The thing is, the Cabinet Manual does have a section about ministers upholding and being seen to uphold "the highest ethical standards" at all times, not just when doing ministerial business. Ardern has all the ammo she needs to give Peters a dressing-down over this, but instead she defers. Things don't have to be illegal to be wrong.

Worse, this rot of silence has also infected the Green Party, which, as a confidence and supply partner, has plenty of legitimate room to criticise such tactics. You don't need to tear the Government up or demand that Peters is fired – you can just say what the journalists' union said on Friday, that Peters needs to explain himself and apologise.

Instead the Greens just talk about how the law needs to be changed – which most people agree with, but isn't the point. The topic at hand isn't underhanded but lawful behaviour, it's stuff that is potentially illegal – hence the police referral. The party should grow back its spine.

It is blindingly obvious why Ardern is so blind to Peters' actions. He is not the kind of man to take a telling-off sitting down, and it would probably all get messier as Peters extracted some kind of utu for her daring to criticise him.

But she is the leader of this Government, and of a party that is vastly larger in both power and popularity. Her words set the standard of behaviour for ministers – she is in this sense the most powerful political pundit we have. It's well past time she found that voice.