The government is being warned against introducing a pre-departure COVID-19 test for desperate New Zealanders attempting to get home from high-risk countries.

Yesterday, the government announced an extra day one COVID-19 test, in addition to the day three and 12 tests, as an extra layer of protection amid new variants of the virus emerging overseas.

Those tests will begin being taken from December 31.

It's the idea of a pre-departure test though that has some scratching their heads.

Keeping the virus out of New Zealand and more-to-the-point - the community - remains the government's priority. The new proposal of a pre-departure test would cover people travelling from Britain, where they've gone back into lockdown because of the new variants of the virus.

Anyone required to get a pre-departure test would have to pay for it themselves.

Microbiologist Siouxsie Wiles says that may create unfair barriers.

Microbiologist Siouxsie Wiles Photo: RNZ / Dan Cook

"The problems with requiring a test is where do people get a test, how available is it to get a test, and how reliable are the tests that people get... and then there's the problem of who can afford the test," says Dr Wiles.

It may not stop the virus either, she says.

"There's no guarantee that when you get tested and you test negative, that you then wouldn't become positive en route to the airport, or on the plane."

Minister for COVID-19 response Chris Hipkins calls the pre-departure test an extra hurdle, and says it has not been considered lightly.

The government would not leave people in the lurch, he says.

"We would give people notice before we hit the go button,” says Hipkins. 'There was still a lot to figure out and get sorted.

"If you're travelling from London, for example, you might be travelling to somewhere that doesn't require a pre-departure test in order to then onward travel to New Zealand - and so they're not necessarily going to be checking your pre-departure test in London, and that creates an interesting challenge for us that other countries who are imposing this requirement don't have."

The pre-departure measures could be in place from mid-January.

The National Party had been calling for pre-departure tests to be added to the country's defences against COVID-19, and its spokesperson Chris Bishop told ‘Morning Report' the government's move was a step in the right direction.

National Party COVID-19 Response spokesperson Chris Bishop Photo: RNZ / Dom Thomas

But they needed to go even further and make it a requirement for all arrivals rather than just those from Britain, he says.

"We've simply got to keep COVID out of New Zealand, the prospect of more lockdowns and more community transmissions in New Zealand is not something I think anyone listening would want and we simply have to have a hard line."

Bishop says he understands the concerns about being able to access a test, but doesn't believe that was the biggest barrier to coming here at this stage.

"I think there are legitimate concerns around that but the biggest barrier to coming back to New Zealand at the moment is not being able to get a COVID test, the biggest barrier is going through MIQ ... there are no spots available until March,” says Bishop.

"The obligation is on the people coming back to New Zealand to go and get a test. Our border is our first and best defence against COVID and this essentially extends the border our offshore as well. The simple reality is that COVID is spreading around the world, particularly with this new strain that a lot of people are really worried about."

He says a trans-Tasman bubble needed to be set up as soon as possible to free spaces in managed isolation.

Asked whether National would look at extending help to those struggling to leave Britain or other countries, he says that was something that would be looked at in time.

- Jonathan Mitchell/RNZ