The Fiji-based Pacific Concerns Resource Centre, the PCRC, says the Pacific Islands countries will continue to lose influence in the Forum if it allows French Polynesia to get observer status.
While French Polynesia has a new autonomy statute within France, it wants to become the first Forum observer that is not seeking independence from its colonial ruler.
The PCRC's Peter Emberson says Pacific countries are exposed to French cheque book diplomacy, with Niue now supporting the French Polynesian bid.
And he says the Forum now appears to be controlled by Australia and New Zealand interests.
"This is opportunism at its best. Now that New Zealand is the chair, and it seems as it it's an opportune time to change the rules, the long-standing rules. The Pacific Islands Forum is like an institution that's controlled by Australia and New Zealand and now it looks as if European countries, such as France, would have a greater stake in the say of what was a Pacific Islands platform."
Peter Emberson of the Pacific Concerns Resource Centre