Transparency International in Vanuatu says an amendment to the Public Service Act will return the country to the instability of the 1990s.
Parliament last week passed an amendment to the Act, which means the head of public agencies will no longer be appointed by the Public Service Commission, but by ministers.
Transparency's president, Marie Noelle Ferrieux Patterson, says it removes the independence of the public service, and directors general will be beholden to politicians.
She says the heads of ministries provide continuity even when the government changes.
"There was no discussion at all, there was just, I think probably, rising tensions in the last few years, because ministers didn't get to do exactly what they wanted, sometimes they had a voice or reason behind, or someone who was knowledgeable who could tell them what the law was, if they were tempted to go astray."
Marie Noelle Ferrieux Patterson says Transparency International is getting legal advice on whether the move is constitutional.