Elizabeth Ponga of the Group for Political Change in the Cook Islands has questioned whether all MPs do enough work to earn their recent salary increase.
The increase was approved in April but was only made public by the Ministry of Finance this week.
It sees an MP's base salary jump from 26,000 to 36,000 US dollars while the Prime Minister's salary goes from 56,000 to 79,000 US dollars.
The pay hike follows an amendment in March to legislation governing the Remuneration Tribunal, giving the finance minister and cabinet the final say in setting MPs' salaries.
Ms Ponga says the problem is not so much about government ministers, who carry a bigger workload.
"But its the other members that are only kind of there, and then they go back and do their own businesses. While they're working for their own businesses, they're still being paid that lump sum of money per annum. So how do you justify that? You get one for free - don't have to sit in the office and then you conduct your own business. That's where it's unfair."
Elizabeth Ponga of the Group for Political Change in the Cook Islands