Consumer New Zealand says its research shows there is little to be gained from joining a credit card rewards scheme.
The watchdog group is urging average spenders and those who do not pay their credit card off in full each month to avoid such schemes.
It says its biennial study has again shown people need to spend a lot to reap any rewards.
As part of the research, it spent $25,000 on a credit card over two years, paying the bill in full each month.
But the group says it did not even earn enough points to buy a $500 trans-Tasman flight.
Consumer New Zealand says with many cards, people need to spend at least $12,000 a year and pay the card off in full each month just to cover the fees.