Dr Ashley Bloomfield says the "stamp it out" phase for Covid-19 will be in place as long as is necessary.

Outgoing Police Commissioner Mike Bush has come under fire for withholding police guidelines being used to enforce the lockdown.

A leading disaster law academic says the secret advice is "in effect the rules, the law at the present time", so the public had a right to know what discretion is being exercised.

Dr John Hopkins from the University of Canterbury also cautioned new laws for social distancing would have to be created after the lockdown.

Hagen Hopkins Outgoing Police Commissioner Mike Bush, confirmed during a meeting of the Epidemic Response Committee that he received advice from Crown Law about how police officers should use their new powers.

Bush, who appeared at a meeting of the Epidemic Response Committee on Thursday, confirmed he received advice from Crown Law about how police officers should use their new powers.

The select committee is acting as a replacement for Parliament during the lockdown and is being chaired by National Party leader Simon Bridges.

ROBERT KITCHIN/STUFF A leading disaster law academic says the secret police advice is effectively acting as the law, so the public have a right to know what discretion is being exercised.

When asked what was in the guidelines, Bush told the committee that how they were applied was a moving feast.

When Bridges asked if Bush would make them publicly available, the commissioner said he would take advice from the Solicitor General.

Bridges said there was a need for clarity and certainty alongside the discretion police had. Even a public summary would be helpful, he said.

NZ Parliament/VIMEO Dr John Hopkins from the University of Canterbury Law School told the Epidemic Response Committee the Government should now be thinking about a law change for social distancing.

The committee raised serious concerns about how well the lockdown was being policed, Bridges said.

Hopkins, a professor at the University of Canterbury Law School, specialising in law and disaster, told the committee many of the powers of the lockdown appear to be exercised under the Civil Defence Emergency Act.

Reliance on this act was problematic because it was highly discretionary.

POOL VISION Commissioner Mike Bush says police can track those returning from overseas through their smartphones, but only with their consent.

"It is not in my view sustainable in the longer term, it risks conflict."

An example of this could be seen with the mixed messaging the past few days of the lockdown, Hopkins said.

There was currently nothing between the primary law and the officers on the ground and he urged Bush to make the guidelines public.

The other powers being used by the government in response to Covid-19 included the Health Act 1956 and the Summary Offences Act 1981.

"The legislative framework, to be absolutely frank doesn't appear to envisage the type of lockdown the government has introduced under advice from experts ... This has led to a degree of confusion."

Police officers were currently working under guidance, supplied by the police commissioner and Hopkins suggested they should be made public.

"They are in effect the rules at this present time, so we should know how that discretion in being exercised.

Once public, they needed to be examined by the select committee to make them legitimate and publicly acceptable, Hopkins said.

"The public airing of rules exists for a good reason."

The discretionary powers were suitable for a narrow timeframe of an emergency but not for disaster recovery in a democracy, he said.

Once the state of emergency has ended the country will have nof choice but to move down the regulatory role.

"It is less clear if the Health Act will support the countrywide social distancing that will remain necessary for months to come."

Settling in for the long haul, the Government should now be thinking about a law change, he said.

Keeping everyone on board would require a move away from the emergency phase and the natural instinct of leaders to use discretion.

ACT Leader David Seymour said police had an opportunity to encourage respect for the law by being open and transparent about how its officers will use their new powers.

The advice needed tp be released, because police had extraordinary powers at present and a large degree of discretion in how officers used them.

There was also a level of confusion about what New Zealanders can and can't do during the lockdown.

The Commissioner's recent language also created some concern about whether the rule of law is being upheld, he said.

"The rule of law requires that rules are clear and publicly accessible. That is not the case at present."

"Police can't demand respect from the public but must earn it. Police have an opportunity to encourage public respect for the law by being open and transparent and releasing Crown Law advice. New Zealanders need to know how police's extraordinary new powers are being exercised," Seymour said.