A security guard who tested positive last week was previously last tested in November last year - six months ago - even though he is meant to be tested every fortnight.
The information has emerged during the health select committee this morning, when MBIE chief executive Carolyn Tremain said the last test in their system was from November.
She said the security guard was a relief night-shift worker - who are still meant to be tested every fortnight - who worked regularly as opposed to casually.
Tremain is fronting the committee this morning with director general of health Ashley Bloomfield and head of MIQ Brigadier Jim Bliss.
She said there were inconsistencies across the whole recording system for border worker testing, and MBIE was working to make sure it was complying with the public health order requiring the frequent testing of border workers.
The guard may have been tested more recently than November - but if so, it wasn't in the system.
Tremain said 89 per cent of 4000-odd MIQ workers had now received their first vaccine jab.
National Party Covid-19 response spokesman Chris Bishop asked: "How many workers have missed tests they should have had in the border workforce?"
Tremain said she didn't know.
MIQ deputy chief executive Megan Main added: "No, we don't know the exact number. We're working towards a mandated system next week ... the 300 or so employers in MIQ will have the ability to look at percentages of compliance and non-compliance in a more robust way."
Questioned about the lack of testing for the Covid-positive worker this morning, National leader Judith Collins said she was "floored" by the revelation.
"The public has been promised for months that all of the frontline border facing staff were being tested regularly.
"Now to find out he [the security worker] hadn't been tested for months - it's just unfathomable."
The committee became feisty when Bishop asked for more time to ask one more question, adding that the session started with a "20 minute lecture".
He was granted one more question, and later moved a motion to have the session extended for an extra hour.
"I've moved a motion before the committee. You are required to put that to a vote."
Committee chair Liz Craig then closed the session.
Their appearance comes hours before the weekly vaccination update from Covid-19 Response Minister Chris Hipkins, who is expected to release new data about which border workers have and have not been vaccinated.
Bloomfield has remained adamant that the vaccine roll-out is more or less on track. At the last update - a week ago - almost 20,000 people had received two doses of the Pfizer vaccine, while 71,000 had had one jab.
But the Government has been increasingly on the back foot over its reluctance to release data including daily vaccination doses and targets, and the proportion of frontline border workers who are still to be vaccinated.
In the past week, two security guards at the Grand Millennium MIQ facility caught Covid-19 and weren't vaccinated - even though they are supposed to be at the front of the queue.
This morning the Herald revealed the Ministry of Health is urgently seeking 18 "crucial" positions for the roll-out, which the National Party says "beggars belief".
"Why wasn't the Government organised enough to recruit these urgent and high priority roles well in advance of now? It is a deeply concerning sign that the vaccine programme is in trouble," said the party's Covid-19 response spokesman Chris Bishop.
And this morning the head of Counties Manukau DHB said Auckland only has half the number of Covid-19 vaccinators it needs for the roll-out.
The Ministry of Health says it needs to scale up its workforce in line with the roll-out, which is currently prioritising border workers, high-risk frontline workers
and people living in high-risk places.
The Ministry of Health has just started releasing the number of vaccine doses compared to the roll-put plan - but only up until the previous week and not looking into the future.
On Monday Prime Minister Jacinda Ardern revealed the number of MIQ workers who have had at least one vaccine jab - 86 per cent - but only after the Government revealed that two infected Grand Millennium security guards hadn't been vaccinated despite them wanting to be.
The Government has also faced criticism for not making its central register of border workers compulsory - which it now intends to do - meaning it did not include the testing history of some MIQ workers from private companies.
Yesterday there were no new community cases, and four border cases including one from India. The Government has temporarily suspended arrivals from India as it looks for ways to lower the risk of importing cases from there.