The Fiji Womens' Rights Movement says the Methodist church could undermine the proposed Family Law Bill through its outspoken opposition.
The movement's co-ordinator, Virisila Buadromo, says 90 percent of indigenous Fijians are Methodist so the church's stance will have a big impact.
Ms Buadromo says it is a government bill and there are the numbers in the house to push it through so long as the MPs remain committed to it.
"The government was voted in by the Fijian voter, so if the Methodist church are preaching from the pulpit that the Family Law Bill is not a legislation that they are going to support, it's quite likely, that it may result in the Bill not becoming legislation."
The former president of the Methodist church, the Reverend Manasa Lasaro, has criticised the Family Law bill which grants equal rights in marriage, divorce and family property, because he says it would destroy a traditional patriarchal society.
The Reverend Lasaro says the church also believes that the bill is against the god-given order that men are head of their families.
The Family Law bill would ensure Fiji meets the requirements of the UN Convention on Children's Rights and the elimination of discrimination against women.