Labour MP Su'a William Sio says he will be voting against the same-sex marriage bill, which he says could cost the party the next election.
The MP for Mangere said there was widespread opposition within his electorate, which has the highest population of Pacific Islanders in New Zealand, making up 58.8 per cent of voters.
Some ministers in Pacific churches were preaching against the bill and against Labour.
''This issue cuts deep into fundamental beliefs,'' he told Radio New Zealand. ''It will divide the community.''
Sio said the bill was causing unnecessary harm to Labour and should be withdrawn.
''There are more weightier and more pressing issues like holding (Prime Minister) John Key to account for the weakening economy and lack of jobs.
''That's where our priority ought to be, rather than an issue that has the potential to really derail our focus on winning election 2014.''
Sio said the gay marriage bill could cost Labour more support than the estimated 30,000 votes it lost in the 2008 election over prostitution law reform, civil unions and anti-smacking laws.
But Labour MP Louisa Wall rejected claims that opposition from crucial but conservative South Auckland Pacific Island voters to her gay marriage bill could cost the party the next election.
The MP for Manuwera had her member's bill pulled from the ballot and it is expect to pass its first reading when it comes before Parliament next month.
It will be a conscience vote and MPs are already being lobbied on the issue by their constituents.
Many Pacific Islanders also live in Wall's electorate, but she says she is not getting any resistance from voters.
However, she had written to all religious leaders, not only Pacific leaders, in her electorate explaining what the bill was about and stressing they would not be forced to perform any gay marriages.
''What I am really worried about is misinformation and propaganda.''
Wall said she ''completely disagreed'' her bill could cost Labour the next election.
''Labour will come out strongly in terms of fighting for the rights of all people. This fundamentally is about human rights and the dignity every New Zealand citizen has to access what is an institution that the state moderates, only the state can give out marriage licenses.''
Having the Pacific community support Labour's bill was important, she said.
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