The National Party is accusing the Government of taking rapid antigen tests away from the private sector to hide its own incompetence.
There are 4.6 million of the Covid-19 tests 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 the director-general of health describes as a very competitive global market.
National Party leader Christopher Luxon told Morning Report, "After months of denying that rapid antigen tests were the go, the Government is now embracing it. That's a good thing.
"The challenge they've got [is] they're scrambling. They have only approved seven, maybe two more ... [types of] tests. Australia, to give you a feel for it, has over 50 approved tests.
"The Prime Minister says we've got 4.6 million in the country. What she doesn't clarify is whether they're in the private sector, or whether they're actually held by government.
"We've got a lot of very good employers who care deeply about their employees who have gone off, use the approved test, secured a supply and brought them into the country and it looks like the Government is actually commandeering that supply and then taking it for themselves and saying it's only available for those that will actually test to work and not actually available freely for everybody else.
"The big problem that we've got is that, yes, we've only got a handful in the country. We have got another order that's due here early March. We've got another order that could possibly be up here in April, May - it's all a little bit too late. So I understand what the Government is doing in terms of trying to commandeer from the private sector.
"But I don't think that's the right thing to have done, because essentially these are companies that have done the right thing by their people, by their employees, got on to it early, seen it happening around the world and getting on to it."
National would be supportive of a test for work scheme to help critical workers and reduce disruption.
"Our challenge is the definition of a critical worker. Our view it should be as broad as possible to make it so that you can keep the disruption as minimal as possible."
If supplies allowed, National would have the tests available for everyone.
"Here's the deal: When does personal responsibility kick in? Let's say you want to go see your grandparents. You'd want to be able to swing past the supermarket, do a quick test and say 'Right I'm good to go see nana and granddad' and that's just someone being sensible - personal responsibility.
"Now, if you choose to take one, you should certainly pay for it. If it's actually free because you're a critical worker and it's about test to work, then that should be freely available to you.
"The other thing that happens, which is really helpful, is that a lot of countries around the world, actually, if you do your test at home, you just upload your results through your app to the government, and the government has that full record."
Rapid antigen tests
Yesterday, Prime Minister Jacinda Ardern said there were nine types of rapid antigen tests (RATs) currently available for use, with another 19 types under a full technical assessment.
The effectiveness of RATs could range from 30 per cent to 80 per cent accuracy, she said.
Asked when people could pick up rapid antigen tests from the supermarket and test themselves at home, Ardern said the Government wanted to make sure the tests were not being used for no reason, especially given the tests had a tendency to produce false positives.
The Government would provide critical workforces with RATs and would support businesses to support their workforces with access to the tests also, Ardern said.
RATs also did not always have long shelf life, she said.
Ardern said the "test to return to work" regime would be used for essential workforces, but government would provide more detail on that today.