Prime Minister John Key is strongly defending the police use of hidden video cameras, rejecting suggestions they knew what they were doing was illegal.

His comments follow scathing comments from some Supreme Court judges in their ruling this month that police covert video surveillance on private property had no legal basis and was, in fact, illegal.

"The deliberate unlawfulness of the police conduct in the covert filming ... is destructive of an effective and credible system of justice," wrote Chief Justice Dame Sian Elias.

But Mr Key said the Court of Appeal had previously ruled that police planting hidden cameras on private property without consent - but with a search warrant - was legal.

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"Those judgements from the Court of Appeal were very clear that video surveillance was admissible and we had no particular reason, as a result of those decisions, and the common law rulings in the last 15 years, to consider that to be anything other than a lawful position."

A bill to make covert video surveillance lawful will be rushed through parliament with a shortened select committee process in the next two weeks.

The Video Camera Surveillance (Temporary Measures) Bill aims to side-step the Supreme Court decision, which will still apply to the Urewera case.

The Government has the numbers to progress it to select committee, but has no guarantee on sufficient support beyond that stage.

The bill will be introduced tomorrow and will be tweaked to ensure that it does not give police broader powers than what they had before; courts will still have the ability to rule camera use unlawful if it breaches the Bill of Rights Act protection against unreasonable search and seizure.

The bill has the support of United Future.

It will have the support of Act and the Labour parties at the first reading, but ongoing support will depend on what comes out of the select committee hearings.

The committee will report back to parliament next Monday and the House will go into urgency on Thursday to pass the remaining stages of the bill.

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Attorney-General Chris Finlayson said the bill would preserve the legal situation before the Supreme Court judgement, as it was understood by "successive governments, police and the Court of Appeal".

"The Bill will mean that Police will be able to resume operations involving surveillance.

Around 50 operations were discontinued after the Supreme Court's decision," he said.

However the judgement will stand in the Urewera case, which triggered the court decision.

Mr Finlayson said he was persuaded that a select committee process was the right thing to do.

Mr Key said some police operations that have been suspended were for alleged serious crimes, including drug offences, and carried a possible life prison term.

Legal commentators and Labour leader Phil Goff have questioned this because the Evidence Act allows improperly obtained evidence to be admissible if a judge thinks it is appropriate.

"What evidence does the Government have that actually 'serious' criminals will get off the hook if this legislation is not passed under urgency?" Phil Goff asked.

"Other legal opinions say quite authoritatively that that won't happen.

"I think having urgency and retrospective effect is getting worst of both possible worlds."

Mr Finlayson earlier rejected a proposal to fast-track provisions of the Search and Surveillance Bill relevant to police use of video surveillance.

"That is a large and complex piece of legislation that is much wider than this particular issue. It would also introduce a wholly new regime for video surveillance, rather than returning to the previously understood status quo like the Video Camera Surveillance (Temporary Measures) Bill, and giving us time to think through the options."