The Council for World Mission says it's going to lobby governments throughout Pacific countries to take action against Fiji.
The comment follows the arrest of several Methodist church leaders and Fiji's most senior female High Chief over the church's annual conference, which the interim government has banned.
The interim prime minister Commodore Frank Bainimarama says those detained are appearing in court this afternoon, in relation to the breach of a permit given to them when they met as a standing committee seven days ago.
Martin Baker of the council's Pacific arm says in many countries the church is a major player in national infrastructure and any pressure on government can have a significant influence.
"I think we have a profound concern to see what appears to be a growing level of religious oppression and especially oppression of a major church in Fiji, I don't think it bodes well for the future. I mean, to alienate a group of that significance seems to me to be a likely cause for growing unrest and increased conflict within that nation."
Martin Baker says he's written to New Zealand's prime minister and the council's management team will meet next week to form a plan of action.