Some non-government and community groups in Vanuatu remain opposed to the Melanesia Spearhead Group's acceptance of Indonesia as an observer.
The MSG this week marks its 25th anniversary organised by its secretariat in Port Vila.
Two years ago, the MSG agreed to grant Jakarta observer status despite protests from many West Papuans who are Melanesians.
Our correspondent, Len Garae, says for many locals, the move goes against the principles of Vanuatu's first Prime Minister, the late Father Walter Lini, who helped set up the MSG 25 years ago.
"It's seen as a slap in the face by NGOs in Vanuatu including the National Council of Chiefs, and women organisations and youth organisations in the country, because they have successfully mobilised the grassroots throughout the country to stand firm with the people of West Papua to demand independence for West Papua."
MSG members are Fiji, Papua New Guinea, Solomon Islands, Vanuatu as well as the FLNKS of New Caledonia, with Indonesia and Timor-Leste joining as observers.