The Prime Minister is isolating after her partner Clarke Gayford tested positive for Covid-19 rather than using the exemption scheme for critical workers for two reasons: their daughter Neve and because she is not technically considered a critical worker.

After Gayford tested positive for Covid-19 on Sunday, some have wondered why the PM could not carry on under an exemption scheme which allows critical workers who are household contacts to go to work provided they test negative each day.

Business and workplaces have to register as "critical services" for their workers to qualify for the scheme – and while the PM could probably qualify for it, it had not happened for ministers or MPs or Parliamentary staff – including the Prime Minister.

A spokesman for the Prime Minister said childcare for her daughter Neve was another reason.

"As has also been the case for many families with children where one partner is sick the Prime Minister has both childcare and caring responsibilities for her other household members."

The spokesman said Ardern was following the same rules as other New Zealanders who have had to isolate and other ministers and MPs, including the Leader of the Opposition.

She did not believe she needed the critical worker exemption.

"The test to return exemption for critical workers was primarily designed to ensure supply lines and essential services were not interrupted – but the general rule remains if somebody can isolate and can do their duties from isolation they should do so in order to stop further chains of transmission."

While Ardern has had to cancel some events – including a visit to Hawkes' Bay – she could do most events and meetings remotely, including chairing Cabinet, delivering a pre-Budget speech to Business NZ on Wednesday and taking part in Question Time and speeches in Parliament.

Deputy PM Grant Robertson will fill in for her in the daily media stand-ups and press conferences, although she has done her regular one on one interviews by Zoom or phone.

The wisdom of keeping MPs out of the exemption scheme could be tested if Robertson found out he was a household contact on Budget Day – but many MPs in the Omicron outbreak have stayed home, either with Covid-19 themselves or for household members.

That is why Green MP Elizabeth Kerekere was reprimanded by her party for travelling to Wellington when she had a Covid case in her household – she had mistakenly thought she came under the exemption.

Speaker Trevor Mallard said no party had asked him to advocate to register MPs under the scheme.

Steps such as allowing MPs to take part in Parliament virtually – including speaking and voting - meant they could now do a significant part of their job from home unlike the lockdown periods of the past.

Examples of workers considered "critical services" listed on the Covid-19 website are food production and its supply chain, key public services such as health and emergency services, lifeline utilities such as power and water supplies, transport, critical financial services, news media, social welfare and health and animal health workers.

Parliamentarians were considered essential workers during earlier lockdowns in 2020 and 2021 when the elimination strategy was still running. At that point, there was no system to take part in Parliament remotely.

The former National Party leaders Simon Bridges and Judith Collins both came to Parliament during lockdown periods when regional travel was otherwise forbidden – but the rules were different at that time – the lockdowns were aimed at halting small outbreaks and they were not household contacts.