The Ministry of Health has requested a quote for 6 million new syringes for the Covid-19 vaccine, with a requirement that 3 million arrive by the end of this month.
The ministry said it had already ordered enough syringes for the entire vaccine rollout, but confirmed that a particular combination of needle and syringe has meant just five doses being extracted from each vial of vaccine.
Ministry guidelines say vaccinators should "expect" to get six doses from a vial.
National's Covid-19 spokesman Chris Bishop said the order looked "very last minute and not at all consistent with a well-executed plan to effectively and efficiently administer vaccinations to New Zealanders".
A spokesperson for the ministry said the order was to "seek quotes for different brands of syringes and needles as part of our ongoing contingency planning."
The ministry said there were brands of syringes on the market that may make it easier to get seven doses of vaccine from a vial of vaccine rather than six or fewer doses.
Bishop said the late order was "concerning".
"Why has a supply of syringes not been sorted out well before now?"
Bishop said he wanted to know about the "performance issues" with the current stock that was leading to fewer doses being extracted per vial.
The ministry opened up the process for quotes last Thursday and has set a deadline for August 11, meaning whoever is successful will have just weeks to deliver millions of syringes.
The ministry wants the remaining 3 million syringes to arrive by the end of September.
The number of doses the Government "expected" to extract from each vial has changed over the course of the rollout.
The first shipment of vaccines ordered by the Government in January was expected to deliver five doses per vial, but this was later updated to six.
In April, the ministry's Vaccine Operating Guidelines were updated to say the "expected" number of doses able to be drawn from each vial of vaccine was six.
The guidelines go on to say that technically, it was possible to extract seven doses from each vial. Some vaccinators in New Zealand have been able to get seven doses from a vial.
The vaccine rollout is meant to ramp up significantly in August. As of July 27, New Zealand had administered 1.7 million vaccinations - but by the end of August this number is meant to nearly double to more than 3 million.
The pace is set to continue ramping up with the Government administering 5.4 million doses by the first week of October.
Over the weekend, the Government hosted New Zealand's first max vaccination event, which saw more than 10,000 people jabbed over three days at South Auckland's Vodafone Events Centre.
Vaccinators were hoping to average a jab every 90 seconds working across 240 booths at the centre.
Covid-19 Minister Chris Hipkins referred requests for comment to the Ministry of Health.