President of Young National Sean Topham said members from around the country had been lobbying National MPs to vote in favour of marriage equality.
"Our generation overwhelmingly supports marriage equality and the Young Nats have been lobbying our MPs to support this bill from day one. We believe in freedom and equal opportunity for all Kiwis, and our generation clearly agrees."
Young Labour spokesperson Sam Thompson said marriage equality and adoption reform were voted as the number one policy priority at the Young Labour conference.
"We believe this is a human rights issue and a generational one. If our representatives in Wellington really value equality and a fair go, they'll make a commitment to expand the right to marry to everyone who has a partner they love and want to spend their life with," said Thompson.
Young Greens' spokeswoman Izzy Lomax said they were pleased all 14 Green MPs will vote in favour of marriage equality.
She hoped MPs from other parties will also vote strongly in favour.
"Young Greens believe in a society without discrimination, and we want to see an end to all discrimination against rainbow communities, starting with allowing loving same sex couples to marry," she said.
Mana Rangatahi spokesman Ian Anderson said Mana Rangatahi's policy is in favour of marriage equality. Mana leader Hone Harawira will be voting in favour of the bill at its first reading.
Act on Campus spokesman Hayden Fitzgerald said Act on Campus were long-time supporters of marriage equality, and are delighted that so many MPs will be voting in favour of Louisa Wall's bill.
"ACT on Campus has long held the view that there should be one law for all. We believe marriage equality is a key part of achieving this."
A Colmar Brunton poll conducted in May this year revealed 76 per cent of New Zealanders were in support of marriage equality.
