The owner of one of the country's busiest supermarkets says he would "struggle immensely" under the Labour Party's immigration policy.

Through targeting low-skilled workers, students in low-level education courses, and making sure "employers hire Kiwis first", the party plans to reduce immigrant numbers by up to 30,000 a year.

Jason Witihira, the owner of New World Victoria Park in Auckland, said if he was forced to employ New Zealanders in low-skilled jobs such as stacking shelves, it could result in such a staff shortage he would have to reduce his store's opening hours.

"You advertise the jobs to all New Zealanders, and predominantly, it's migrants that are applying," Mr Witihira said.

"I'd struggle immensely. The first people I want to give a job to is New Zealanders, whānau first, but at the end of the day, you can open the door but you can't force them to walk through it.

"The hours of work or the time of work, [immigrants] aren't questioning, whereas the New Zealand residents don't want to start at three in the morning, or don't want to finish at 12 at night.

"It's not as easy as what some people think."

Labour Leader Andrew Little has previously said he does not believe employers when they say they cannot find New Zealanders to do jobs like stack shelves.

Responding to questions, Prime Minister Bill English accused Mr Little of being "demeaning" about shelf stackers: "If you go to the supermarket and there's no shelf stackers, there's nothing on the shelf to buy, that's a pretty fundamental process in an economy," Mr English said.

Mr English was asked if stacking shelves was a skilled job.

"Go and ask the shelf stackers," he said.

'It's wrong to put someone in a box'

Photo: RNZ / Brad White

Gagandeep Singh, or Gaga as he's known to friends, came to New Zealand from India in 2009 to study - eight years later he has no intention of leaving.

"Slowly, slowly, it made me feel like a country where I want to live," he said.

He started out stacking shelves on 10 to 12 hours shifts at New World Victoria Park in 2012, and is now a grocery manager. A walkie talkie crackles constantly on his hip.

Mr Witihira said Gaga was one of his hardest workers.

But under Labour's new policy, a future immigrant like Gaga would find it incredibly difficult, if not impossible, to start at the bottom and work his or her way up.

"It's wrong to put someone in a box.

"Look at the owner operator of [Pak N Save Pukekohe], he started pushing trolleys," said Som Kadam, the supermarket's bakery manager.

"[Labour's policy] is just the wrong philosophy mate. I started scraping trays and now I manage 17 staff."

Som Kadam lives in Manukau with his wife and two-year-old daughter. From India, he said immigrants should be judged on how hard they work, not what job they're doing.

"If we can't find the people locally, and can't train them up or get them on to the work fast enough, then we need to fill the gaps, who's going to work?

"Who's going to put the product on the shelves, you know? It's a business, so we have to sell the product, if we don't have the product, what are we going to sell, empty shelves?

"The government gets revenue from selling products, GST, how is it going to get the money if there's nothing on the shelves?"

Mr Witihira said he hopes immigration policies allow him to employ migrants, not just for business reasons.

"I respect the government for their decisions, and they've got to make some hard decisions, for the benefit of all New Zealanders, and that's their job.

"I don't disagree black and white, it's just that when you're in business and trying to create a culture of unity and moving forward and serving your community that's diverse as well, it gets a bit hard sometimes."

But Mr Little is defending his party's policy, saying it would not result in supermarkets struggling to fill vacancies.

He told Checkpoint with John Campbell the policy would make sure more New Zealand workers were ready to work.

"We've got 90,000 young people not in work, education or training - over 30,000 of them in Auckland alone.

"I have a moral duty as a political leader to make sure we are doing everything we can to get those people who are already living here a chance and an opportunity to get in the job market and do something," he said.

Mr Little said work visas should match skills shortages.

