Katherine Rich, chief executive of the Food and Grocery Council, which represents businesses that supply shops with food and drink, said multiple members of her organisation had been told their suppliers had been cancelled.
"They have been told that all available stock has gone to the Ministry of Health," she said.
Rich said that businesses were frustrated that they had done the right thing by planning ahead, only for the Government to take their stocks at the last minute.
"They have had plans, they have done the right thing, they put the orders in.
"This idea that RATs are readily accessible is wrong - their orders have been in the country, but they're not able to be dispatched because they've been poached by the Ministry of Health. So much for asking everyone to be prepared."
National's Covid-19 spokesman Chris Bishop said he had also received calls from people who had their tests requisitioned.
He said it was a "stunning indictment of the Government's incompetence over rapid antigen testing".
He said the episode raised further questions about the number of tests the Government has promised it can fulfil.
"How many of the 4 million rapid tests currently in New Zealand, that the Prime Minister has been talking about, actually belong to the Government?
"How many of the 14 million tests the Prime Minister says are on order to arrive by the end of February are actually just orders taken from companies?" he asked.
He blamed the Government for the episode, noting the irony that the Government was now scrambling for tests after banning their importation for most of the past year.
"One of the things we have been working on is how to maintain the food and grocery supply and everybody last year was planning ahead, updating their pandemic plans to deal with Omicron - but eleventh-hour changes like this makes it that much more difficult," he said.
Rich said businesses were now having to explain to the staff who had been promised the tests that they would be unlikely to be able to get them at all.
She was concerned a lack of tests could cause Australian-style supply chain disruptions.
"There are a limited number of shifts that can be sent home before you have to say 'that's it' and you close the whole facility," Rich said.
InScience, which supplies tests, updated its website to say that last Friday the Government "seconded all product held in NZ by the manufacturers of approved Covid 19 RAT product".
They said this limited their own stocks and it would be 3-4 weeks before the next product landed in New Zealand.
Another company, Health Works Group, a supplier of health products, informed its customers via its website that the Government had "seconded incoming stock of rapid antigen test products".
"We have not yet been informed when any stock will be available, so all sales of RAT test products have been paused indefinitely."
Health Works' director Clair Connor said she did not know what legal mechanism the Government was using to get the tests from suppliers that had previosly committed to supplying her company.
"They're seizing the tests direct from the supply companies," Connor said.
"All that's happened this morning is we got a call from our big supply company Roche saying 'sorry, we know we said your order was going to come yesterday, but sadly there is no stock today'," she said.
Act leader David Seymour said the requisitioning of tests showed the Government was not confident in its own supply.
"The Government promises it will have an adequate supply of tests, but clearly does not believe its own spin.
"If it was confident in its own supply, it would not need to confiscate other people's supply.
"At exactly the time when we need to maximise availability of Rapid Antigen Tests to New Zealanders, the Government has effectively told the whole country not to bother importing them because it will take them anyway. There will be fewer Rapid Antigen Tests available thanks to this draconian move."
The Ministry of Health was contacted yesterday for comment.
