The former Solomon Islands prime minister, Ezekiel Alebua, says the involvement of Indonesia in Melanesian Spearhead Group is a mistake.
Pacnews reports that Mr Alebua feels current MSG leaders have diverted the group's founding values by inviting non-Melanesians to have an influence in Melanesian politics.
At its leaders summit in Honiara this week, the MSG is expected to make a decision on a West Papuan bid for full membership.
However, MSG leaders have signalled that the bid will be knocked back, while Papua New Guinea and Fiji have suggested Indonesia's current MSG observer status be elevated to associate member status.
Mr Alebua, who was in power at the time of the MSG's inception in 1986, says the bloc was founded on the values of promoting Melanesian heritage, cultures, and traditions, to maintain peace and harmony and ensure prosperity in the region.
He leaders of Fiji and Papua New Guinea seem to be more interested in trade and commerce than these values.
Mr Alebua urges the MSG to seriously consider West Papuan membership, saying the indigenous Melanesians of Indonesia's eastern region are being abused and tortured, and so the MSG must act morally.