Not soap, hand sanitiser, bread or toilet paper.

Instead, it's the humble cauliflower.

A government-initiated 'price watch' form set up to get public feedback has revealed the vegetable is the number one issue for Kiwis as they stock up through the lockdown.

Prime Minister Jacinda Ardern said in the first day of its operation, 990 submissions were made and one message was coming through loud and clear.

"The most common complaint was ... the high price of cauliflower," Ms Ardern said, struggling to deny her smile at the news.

Kiwis have told the government they've been asked to pay $NZ13 ($A12.65) for a single cauliflower during the lockdown.

"We are taking these complaints seriously," Ms Ardern said.

Supermarkets are on the front line of New Zealand's shutdown, with butchers and greengrocers all shut down, along with restaurants, which have not even been allowed to offer takeaway or delivery.

That's placed a huge burden on the major retailers, which have employed thousands of extra workers to manage the demand.

Around the country, supermarkets have set up lines in their car parks for people to wait for entry.

During peak times, Kiwis are waiting - with a two metre distance either side of them in line - for up to an hour to head in and buy their goods.

And while the government and eagle-eyed New Zealanders are on high alert for price gouging during the lockdown, industry sources suggest there's little sinister about the cauliflower price.

A relatively hot summer in New Zealand, with little rain on much of North Island's agricultural land, has reduced supply of the Mediterranean favourite.

Ms Ardern said she - and the eagle-eyed Kiwis on the price-watch beat - would remain diligent.

"In some cases, it will simply be an issue of constrained supply, particularly when it comes to produce," she said.

"But we are investigating complaints that are made because this is a time when we want to know that New Zealanders are being treated fairly."

Australian Associated Press