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

Police officers are being told they must suspect someone has coronavirus to enforce the lockdown.

A police guidelines document, seen by Stuff lists scenarios police have no power to do – such as pulling over cars or entering properties to check lockdown compliance – unless they believe a person there may have Covid-19.

ROBERT KITCHIN/STUFF Police have released updated guidelines around Alert Level 4 rules and provided clarity around what was acceptable bubble behaviour.

The document, titled Operational Policing Guidelines - Alert Level 4, scenarios for the Frontline, was issued to staff on March 28 by Police National Headquarters. Police Commissioner Mike Bush has since come under fire for not making the guidelines public.

The guidelines appear to contradict Prime Minister Jacinda Ardern's comment on Sunday that "the police have all the resources they need to enforce the lockdown, including the power to arrest and detain people, if need be."

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While police have been doing spot checks on people in mandatory isolation, such as returning travellers, as well as checkpoints, the guidelines suggest those powers do not extend to those are well and unlikely to have the virus.

Of the three people police arrested for "persistent" lockdown breaches, two were detained before being released without charge, and the other was held to face pre-existing charges.

National Party leader Simon Bridges said he would support expanding police powers – even if it took a law change to do so.

"It's increasingly clear that neither the guidelines or the law allows police to enforce the lockdown," he said.

WHAT THE POLICE GUIDELINES SAY

The document starts by telling officers there is no curfew in place, and people are still allowed to move around as long it does not have the potential to further spread the virus.

It notes there is no power to stop vehicles to check the occupants are complying with the Covid-19 health notice.

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.

Police are reminded that at all times they need to apply "common sense" and understand the intent of what they are asking people to do.

Police are given four steps: engage, educate, encourage, and enforcement such as warnings or arrests, with the latter only to happen if "absolutely necessary".

The document includes a summary of the health act and civil defence emergency management act powers for responding to Covid-19.

Isolation was not part of the Medical Officer of Health's (MOOH) notice, with the Government relying on voluntary compliance to stop cars, enter properties or give directions.

If a serious incident arose involving failure to isolate, officers were advised to call the National Command and Coordination Centre, who would then contact the MOOH for a notice.

ANDY JACKSON/STUFF Police check out people surfing at Back Beach in New Plymouth. They left without telling surfers to leave the water.

However, police do have the power to enter a property under the Civil Defence Emergency Act to enter a home if they believe someone with Covid-19 is not isolating.

Police also have the power to direct someone to go with them to a medical facility if they deem they may have Covid-19.

The document gave staff a list of scenarios to help.

TEEN PARTY SCENARIO

In this scenario, police are called to a teenage party in a suburban house, with no parents home. This is not covered by the health notice as it is at a private address.

The occupier says they are a group of friends who – bar one – live together and are having a low-key gathering and hurting no-one.

To exclude the friend, "you would need to determine whether you believe that this situation is one where there is a substantial public health risk (for example if someone was displaying symptoms of Covid-19, were known to have Covid-19, or had recently returned from overseas)".

Dom Thomas/RNZ National Party leader Simon Bridges called for the Government to release both the guidelines and advice from Crown Law.

JOGGER SCENARIO

In this scenario, police encounter a person or group who drove to go for a run, cycle or surf.

"There is no enforcement power available as long as they are maintaining physical distancing from each other," the document says.

"People engaging in a leisure or fitness activity within a reasonable distance of their home whilst maintaining appropriate physical distancing is reasonable in the circumstances."

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

COUPLE IN A CAR SCENARIO

Police pull over a couple in a car who do not live together. The driver says they were food shopping and he will drop his girlfriend off on his way home. Neither show coronavirus symptoms.

All police can do is speak to them about keeping themselves safe because there is "no significant public risk".

NEW POWERS

Bridges, who chairs the Epidemic Response Committee, said if police needed additional powers to effectively enforce the lockdown, he would support it coming back to parliament for a vote.

The guidelines tallied with his understanding of the legal advice from Crown Law to the Government.

"We're hearing from a number of police how uneasy they are about being expected to do things that aren't permissible under their guidelines or law.

"It's incredibly unfortunate. The Government can't expect the police to enforce lockdown when police don't have the power to do so."

He called for "transparency and openness", and asked the Government to release both the guidelines and their legal advice.

Lawyer Nigel Hampton QC said it was "vital" for the public to understand what powers police had.

"These are extraordinary times and extraordinary powers are being used or are available to used."

"You don't want the powers to be more than is necessary, because that's when you start to roll into unwarranted dictatorial state territory. It's got to be kept to the very minimum necessary to ensure public health and welfare."

Dr John Hopkins, a professor at the University of Canterbury Law School, specialising in law and disaster, said most people would follow the rules.

"The problem at the moment is we get mixed messages."

New Police Commissioner Andrew Coster was confident his staff had the power to enforce the rules "within the range of mechanisms available to us". He did not see a need for legislative change.

"I believe we have at hand what we need for what we are seeing in the community at the moment. And we are in an ongoing conversation with health officials about whether further clarity is required for the public and our people."

Ensuring the public understood why the restrictions were needed and being enforced was a "balancing act", Coster said.