Fiji's Foreign Minister, Ratu Inoke Kubuabola, made the comments following the opening of the Pacific Islands Development Forum (PIDF) Secretariat in Suva.
The interim Prime Minister, Rear-Admiral Frank Bainimarama, said the PIDF better represented the region.
"Fiji no longer believes that the Pacific Islands Forum, in its existing form, adequately serves the interests of all Pacific Islanders," he said.
"Fiji wants a fundamental re-alignment of the Pacific Islands Forum before it considers rejoining that organisation."
The PIDF was established in 2012, three years after Fiji's military-backed regime was suspended by the Pacific Islands Forum for failing to return the country to a democracy in 2009.
Refusal to join
At the secretariat opening, Admiral Bainimarama said the Fiji-based group had a single purpose.
"It is not a question of prestige or establishing yet another talk fest, it is about creating an organisation that is more attuned to our development needs as Pacific countries. It is about creating an organisation that is relatively free of interference from outsiders."
On PIDF's website, many member nations of the Pacific Islands' Forum, as well as the United States and French Pacific territories and protectorates, are listed as being eligible for membership.
Australia and New Zealand are notable omissions.
The Australian Parliamentary Secretary to the Minister for Foreign Affairs, Brett Mason, says he welcomes further discussion with Fiji on how the Forum can better serve the region.
"Every nation in the Pacific recognises that Fiji is an important country in the region and we look forward to its return to the Pacific Islands Forum."
Australia and New Zealand recently dropped travel sanctions on all members of Fiji's regime and its military, which had been in place since the coup.
The decision is part of efforts to restore relations with Fiji in recognition of its progress towards democratic elections, with the country heading to the polls on 17 September.