Consumer New Zealand believes Jetstar should not have taken some bookings for flights it is now cancelling.
The airline says the cancellations are due to the Covid-19 situation and travel restrictions and is offering affected customers a credit voucher.
But Consumer New Zealand chief executive Jon Duffy said there is an issue with recent bookings.
"Jetstar was fully aware that those restrictions could be in place when they took the booking and therefore the cancellation of those flights is not outside the control of Jetstar because this is a choice that Jetstar's making."
Duffy said if Jetstar was fully aware that the restrictions were in place when it took the bookings, it would have to give a refund under the Consumer Guarantees Act.
He said the airline has obligations to its customers.
"At the very least they should be entitled to be transferred onto an equivalent flight if Jetstar's got a similar flight available at no extra charge, but if Jetstar can't provide the service that these consumers have paid for, they should be entitled to a refund."
Air New Zealand has also been in the headlines for offering credit vouchers, rather than refunds, on cancelled flights.