Power Play - This week has been a master class in cut-throat, take-no-prisoners politics.

Photo: RNZ / Alexander Robertson

Prime Minister John Key has refocussed public attention on the criminal deeds committed by New Zealanders detained in Australia, and away from their treatment at the hands of the authorities across the Tasman and his government's failure to do much about it.

But at what cost?

The extraordinary scenes of several women MPs rising to their feet to reveal past sexual assaults or abuse, with a plea to Mr Key to apologise for painting them as supporters of sexual offenders, shows how deeply his comments were felt.

Photo: RNZ /Jane Patterson

Accusing fellow MPs, from whatever party, of backing rapists and sex offenders, risks damaging the already delicate reputation of MPs in the eyes of a public cynical of their behaviour and ethical standards.

Interesting too, in light of the fact that only that morning Mr Key had been making assurances the government was doing everything it could to protect the rights of the detainees and to get them home to New Zealand, if that was what they wanted.

Photo: RNZ / Alexander Robertson

Mr Key may have been rattled by Labour MP Kelvin Davis's persistent and personal criticism, but make no mistake - his comments were a calculated political move to position opposition MPs on the side of violent criminals, and the prime minister as the defender of ordinary New Zealanders.

Most people who would sympathise with the opposition MPs' genuine outrage are not likely to vote for Mr Key and his National government.

And Mr Key's accusations would have shored up the support among those who believe the Christmas Island detainees are reaping what they have sown.

Classic wedge politics, carried out in dramatic fashion.

Or, as one senior politician, put it: "political civil war".

Photo: RNZ / Alexander Robertson

Labour Party leader Andrew Little has picked up on the public sentiment and is now subtly moving his position in an effort to deflect the prime minister's strategy.

He is pushing the line the detainees are effectively born and bred Aussies, and that is where they should stay - no-one wants to be advocating for the return of child sex offenders, stalkers and those convicted of family violence.

His MP Mr Davis continues to argue, however, that regardless of what they have done, the detainees do not deserve inhumane treatment; furthermore, he said it will only make it harder for them to settle back into society once they were released.

In another tactic, the release of information, all telling a different story, has been used to muddy the waters.

As often happens, government ministers refuse to release information on all sorts of grounds in response to requests from journalists, until it suits their own purposes.

Photo: AAP

Australian Immigration Minister Peter Dutton released a list of the offences committed by New Zealanders on Christmas Island that was subsequently used by ministers in the New Zealand Parliament.

However, the New Zealand government said no more details could be released to give more context, as the information had been supplied by Australia in confidence.

The prime minister's office here also released a breakdown of the types of offences committed by those waiting deportation from Australia.

That includes 22 people convicted of murder, 16 for rape or sex offences and 34 for child sex offences - however, these were not specific to Christmas Island.

But other questions remain unanswered: for example, how many people have had their visas cancelled under the character provision? This last is highlighted by the case of the former soldier Ko Haapu, who has no convictions but is in detention in Australia awaiting deportation.

His case raises further question about that provision, which the prime minister described as subjective and unfair.

The test under which visas can be cancelled includes past or present membership of a group or organisation, or an association with a person, group or organisation "that the Minister reasonably suspects of being involved in criminal conduct".

Or that your "past and present criminal or general conduct shows that you are not of good character".

Subjective indeed.

So far, Australia has shown no indication it will make any changes to its policy, in response to representations from the highest levels of the New Zealand government and despite Mr Key's view it is unfair.