JOHN KEY: "More than comfortable" with sticking to his support for the bill.

More MPs are showing their hand on gay marriage.

NZ First is pledging not to back the measure and is calling for a referendum. But momentum appeared to be building for enough votes to pass the "marriage equality" bill being led by Labour MP Louisa Wall.

Prime Minister John Key has declared he is "more than comfortable" with sticking to his support for the bill, although it was not impossible he could be swayed into voting against it.

ANDY JACKSON WINSTON PETERS: Fuming.

"What really will be the factor here is do New Zealanders on balance and in the majority think it's the right thing to give everyone, irrelevant of their sexuality, the ability to register their union with another person in a marriage."

However, a small number of National MPs appear to be gathering against it. Cabinet minister Phil Heatley yesterday joined ministerial colleague Chester Borrows in publicly declaring his opposition.

Others, including Bill English, Steven Joyce and Anne Tolley, continue to prevaricate, saying they either haven't given it any thought or want to read the bill before taking a position.

NZ First leader Winston Peters said yesterday his party's eight MPs would not support the bill because it should be the subject of a referendum.