The Prime Minister and Judith Collins will face off in Question Time for the second time this week.
Yesterday, Jacinda Ardern explained why not all border staff were being tested before it became compulsory last Friday.
In answer to questions in Parliament, the Prime Minister said the system was fragmented.
Ardern says they were originally using GPs and a voucher system to do testing - but it didn't enable them to track whether staff had been tested.
She says that's why they moved to onsite testing.
Collins accused the Prime Minister of using "verbal gymnastics" when answering the questions.