The Darleen Tana case continues a pattern of the ‘party-hopping’ law not being applied in instances it was made for – which proves dubious the claims of the law’s backers that it was needed to safeguard public trust in our political system.

Now that Green Party MP Darleen Tana has left its caucus, she becomes the latest elected representative who could get kicked out of parliament under the “party-hopping” provisions in our Electoral Act 1993. But, as with the other recent occasions where this law could have applied, she almost certainly won’t be.

Let’s kick off with a reminder of what this party-hopping (or, as it’s sometimes called, waka-jumping) law says. It requires the speaker of the house (parliament’s referee) to declare that an MP’s seat is vacant in two situations. The first is if an MP expressly tells the speaker in writing that they no longer want to be recognised as representing the political party under whose banner they were elected into parliament.

Call this the self-sabotage option. If an MP gives the speaker the required notice in the required way, they effectively resign from parliament.

The second situation is a bit more complicated. Basically, it empowers a party’s parliamentary leader to give the speaker notice that they reasonably believe a particular MP is acting in a way that has “distorted … the proportionality of political party representation”. Case law then holds that an MP leaving a party’s caucus for any reason automatically creates such a distortion, as it means that political party now has one less seat in parliament.

Call this the party-axing option. If a political party reckons one of its MPs is causing it too much grief, they first can kick the MP out of its caucus and subsequently out of parliament all together. 

However, and this is key, the party leader doesn’t have to take this second step. Should they give the speaker the requisite notice, the MP is gone from parliament altogether. If they don’t do so, the MP lingers on as an independent MP until the next election (when they will get voted out anyway).

And that is what looks very likely to happen with Darleen Tana. After having been forced into voting for the party-hopping provisions back in 2018, the Greens were happy to vigorously flush the taste of that dead rat from their mouths. There seems virtually no chance that they will now use the party-axing option to force Tana from parliament, just as they held back from doing so when Elizabeth Kerekere quit their caucus.

This forbearance continues a pattern where the law on the books simply is not applied in practice. No MP ever has used the self-sabotage option; when they want to leave parliament, they just resign.

Since being reintroduced in 2018, the party-axing option also appears to be a paper tiger that barely even raises a rustle. National chose not to use it after expelling Jami-Lee Ross from caucus because they had strenuously opposed its enactment and so didn’t want to appear to be hypocrites, plus kicking the man while he was so down risked making them look like bullies.

Labour didn’t use the legislation against Gaurav Sharma because they still had plenty of other MPs and didn’t fancy a byelection that they almost certainly would lose. And when Meka Whaitiri found a clever way to get the speaker to recognise her as an independent MP without triggering the party-hopping law’s self-sabotage option, Labour also held off using the party-axing option due to sensitivities about alienating Māori supporters.

All of which raises real questions about the law’s point and purpose. Speaking in the party-hopping law’s third reading debate, then justice minister Andrew Little said this as to why it was needed: “For the public to have confidence in parliament and in our electoral system, it’s the voters who should determine the parties’ share of seats in parliament, and they do that with the party vote during a general election.”

An MP who betrays the voters’ judgment by behaving in a way that changes the balance of seats in parliament therefore has no moral right to be an elected representative. Should they do so, then public confidence in the very basis of our constitutional order demands – demands, I say! – that the MP be removed from their office.

Except… this just isn’t what happens. Instead, whenever an MP behaves in a way that breaks them from their party, that party exercises a purely political judgment. Is it better for us to let the MP stay on in parliament, or to use the party-axing option to force them out of it? 

And, as we’ve seen, the answer routinely is not that “public confidence” requires that the MP be removed from their representative role. Rather, it is that the MP be exiled to the nether regions of independent-MP-land where no one pays them any further attention.

Which then lets us see the real purpose of the party-hopping law. It allows the leadership of each political party to decide the parliamentary fate of embarrassing or troublesome MPs based on their assessment of how it is politically best to proceed. It is a political discipline tool, the use of which depends on individual calculations of cost-versus-benefit to the party itself.

Now, maybe there are good reasons to give the leadership of political parties such a tool to wield over their MPs. But, please, spare us the arguments that this law is needed to safeguard the public’s trust in our political system. Because, if it really is so very necessary, why doesn’t it ever get used?