The government will today outline the next phases of its Omicron response, including its 'test to return to work' approach.

The plan has already attracted criticism, with opposition parties accusing the government of taking rapid antigen tests (RATs) from the private sector and treating the public like children.

With Omicron threatening to topple supply chains, Prime Minister Jacinda Ardern announced yesterday rapid antigen tests were about to play a much larger role.

"Critical workers who are identified as close contacts will be able to use proof of a negative rapid antigen test to return to the work place during their required period of isolation.

"This will minimise disruption to critical infrastructure and supply chains, helping to keep New Zealand going."

More than 4.5 million RATs are currently in the country and another 14.6 million will arrive over the next five weeks.

An additional 22 million have been ordered, but officials are yet to receive a delivery date, in what Director-General of Health Ashley Bloomfield described as a very competitive global market.

National Party Covid-19 response spokesperson Chris Bishop accused the government of seizing tests from the private sector.

"I have been approached by a series of organisations today, all of whom have orders for rapid antigen tests about to be filled. They have been told that those orders cannot be filled because the rapid antigen tests are now going to the government instead.

"That the government has now resorted to requisitioning rapid antigen tests from the private sector is a stunning indictment of the government's incompetence over rapid antigen testing."

The tests will be free and available through community health providers, GPs, and pharmacies.

However, not everyone will have access to them.

"We want to be careful that individuals who just want to check for no reason - they're not symptomatic, they're not a contact, they have no reason to believe they have Covid - that is not necessarily a good use of testing resource. And because rapid antigen tests can produce false negatives and positives, we want to make sure they are being used in the right environments," Ardern said.

ACT Party leader David Seymour says countries around the world were allowing the public access to rapid antigen testing, unlike New Zealand. Photo: RNZ / Angus Dreaver.

ACT Party leader David Seymour said the government was treating the public like children.

"If you want a rapid antigen test, you have to be a critical worker, otherwise you have to stay in isolation for 14 days," Seymour said.

"All over the world, people can go to their supermarket or pharmacy and buy a test to monitor their own health. Here in New Zealand, we have enough on shore for one each, so the government is tightly rationing them."

Associate Health Minister Ayesha Verrall and the Ministry of Health will announce more details on RATs, the treatment of contacts, and quarantine and isolation periods later today.

-RNZ.