ACC is paying some medical specialists $500,000 a year to assess injuries and their independence must be in doubt, the Green Party says.
The specialists decide whether injured people have valid claims, and how much compensation they should receive.
The Green's ACC spokesman, Kevin Hague, says he has documents showing the corporation paid some of its specialists $500,000 a year for assessing between 300 and 500 clients.
"The enormous volume of work and the huge fees paid to these specialists suggests they have been well and truly wrapped up in ACC's processes for delivering its goal to `target the low hanging fruit' - the people with long term injuries," he said on Thursday.
ACC has been trying to get long term claimants off its books, and Mr Hague says it would be "totally unacceptable" if it was using doctors it could rely on to deliver assessments designed to achieve that goal.
"Favouring a select group of specialists whose medical opinions appear to favour ACC's agenda is not being seen to be independent," Mr Hague said.
He is suggesting a rolling roster of hospital specialists to provide assessments.
Mr Hague questioned ACC Minister Judith Collins in parliament, and Ms Collins said she had talked to ACC's new board about the need for robust, independent medical assessments.
She said the same complaints about assessments were being made 12 years ago, when Labour was in power.
Ms Collins said she would discuss Mr Hague's suggestion for a rolling roster with ACC's board.
"I wish to take that matter further and see whether or not it is a realistic situation that we should consider."