Prime Minister John Key wants a new flag, and said he would vote for the Kyle Lockwood-designed Silver Fern (Black, White and Blue).
Very few National MPs went against their leader in their flag choices. Just five out of 59 MPs, including Corrections Minister Judith Collins, will vote for no change.
Cabinet minister Gerry Brownlee, who prefers the silver fern, said he wanted New Zealand to remain a constitutional monarchy, but that "it doesn't hurt" to assert individual sovereignty within that system.
National's Kaikoura MP, Stuart Smith, said Kiwis' fondness for the Union Jack was fading, and was likely to fade further as Britain made it harder for New Zealanders to live and work there.
Labour leader Andrew Little said today he was undecided about his flag preference.
He also said that it was not up to MPs to influence the public vote.
"The referendum is inevitable now and New Zealanders are forming their views ... I don't think it's right for politicians to be skewing the debate even further."
Just one out of 34 Labour MPs, David Shearer, said he would be voting for the silver fern.
The majority of Labour members will vote for the existing flag. Among the flag's supporters were Ikaroa-Rawhiti MP Meka Whaitiri, whose late father was a Korean War veteran.
"Before he passed he reminded me of the importance of the existing flag during his years of service, on many occasions," she said.
Other Labour MPs, including Jacinda Ardern, wanted a new national flag but did not like the alternative option.
United Future and the Maori Party backed a change, though Maori Party MP Marama Fox said she would prefer the tino rangitiratanga flag over the silver fern.
Green MPs had a range of opinions. Five of them would vote for the Union Jack flag, and one would vote for the silver fern.
The others would not reveal their preference, were undecided, or did not plan to vote.
New Zealand First is firmly against a change of flag.
The second flag referendum will be held between March 3 and 24.
In the first referendum, Mr Lockwood's silver fern flag beat four other finalists chosen by a Flag Consideration Panel.
Those five contenders came from a longlist of 40 flags, taken from 10,000 designs submitted by the public.
New Zealand flag: 41
David Seymour - Act Epsom
David Clendon - Green list
Kevin Hague - Green list
Gareth Hughes - Green list
Jan Logie - Green list
James Shaw - Green list
Jacinda Ardern - Labour list
Clayton Cosgrove - Labour list
David Cunliffe - Labour New Lynn
Kelvin Davis - Labour Te Tai Tokerau
Kris Faafoi - Labour Mana
Phil Goff - Labour Mt Roskill
Peeni Henare - Labour Tamaki Makaurau
Iain Lees-Galloway - Labour Palmerston North
Trevor Mallard - Labour Lower Hutt
Sue Moroney - Labour list
Stuart Nash - Labour Napier
David Parker - Labour list
Adrian Rurawhe - Labour Te Hauauru
Carmel Sepuloni - Labour Kelston
Rino Tirakatene - Labour Te Tai Tonga
Phil Twyford - Labour Te Atatu
Louisa Wall - Labour Manurewa
Meka Whaitiri - Labour Ikaroa-Rawhiti
Poto Williams - Labour Christchurch East
Megan Woods - Labour Wigram
Judith Collins - National Papakura
Paul Foster-Bell - National list
Brett Hudson - National list
Simon O'Connor - National Tamaki
Jami-Lee Ross - National Botany
Darroch Ball - NZ First list
Mahesh Bindra - NZ First list
Ria Bond - NZ First list
Ron Mark - NZ First list
Tracey Martin - NZ First list
Clayton Mitchell - NZ First list
Denis O'Rourke - NZ First list
Pita Paraone - NZ First list
Winston Peters - NZ First Northland
Richard Prosser - NZ First list
Barbara Stewart - NZ First list
Fletcher Tabuteau - NZ First list
Silver fern (black, white and blue): 49
Kennedy Graham - Green list
David Shearer - Labour Mt Albert
Te Ururoa Flavell - Maori Waiariki
Marama Fox - Maori Party
Amy Adams - National Selwyn
Kanwaljit Singh Bakshi - National list
Todd Barclay - National Clutha
Maggie Barry - National North Shore
Andrew Bayly - National Hunua
David Bennett - National Hamilton East
Paula Bennett - National Upper Harbour
Chris Bishop - National list
Chester Borrows - National Whanganui
Simon Bridges - National Tauranga
Gerry Brownlee - National Ilam
David Carter - National list
Jacqui Dean - National Waitaki
Chris Finlayson - National list
Craig Foss - National Tukituki
Jo Goodhew - National Rangitata
Nathan Guy - National Otaki
Steven Joyce - National list
Nikki Kaye - National Auckland Central
John Key - National Helensville
Nuk Korako - National list
Barbara Kuriger - National list
Melissa Lee - National list
Sam Lotu-Iiga - National Maungakiekie
Tim Macindoe - National Hamilton West
Todd McClay - National Rotorua
Ian McKelvie - National Rangitikei
Mark Mitchell - National Rodney
Todd Muller - National Bay of Plenty
Jono Naylor - National list
Alfred Ngaro - National list
Hekia Parata - National list
Parmjeet Parmar - National list
Maureen Pugh - National list
Alastair Scott - National Wairarapa
Scott Simpson - National Coromandel
Nick Smith - National Nelson
Stuart Smith - National Kaikoura
Anne Tolley - National East Coast
Louise Upston - National Taupo
Nicky Wagner - National Christchurch Central
Michael Woodhouse - National list
Jian Yang - National list
Jonathan Young - National New Plymouth
Peter Dunne - United Future Ohariu
Undecided: 11
Steffan Browning - Green list
Ruth Dyson - Labour Port Hills
Grant Robertson - Labour Wellington Central
Chris Hipkins - Labour Rimutaka
Andrew Little - Labour list
Nanaia Mahuta - Labour Hauraki-Waikato
Damien O'Connor - Labour West Coast
Sarah Dowie - National Invercargill
Paul Goldsmith - National list
Joanne Hayes - National list
Shane Reti - National Whangarei
Will not say: 10
Marama Davidson - Green list
Mojo Mathers - Green list
Denise Roche - Green list
Metiria Turei - Green list
David Clark - Labour Dunedin North
Clare Curran - Labour Dunedin South
Jenny Salesa - Labour Manukau East
Su'a William Sio - Labour Mangere
Matt Doocey - National Waimakariri
Murray McCully - National East Coast Bays
Will not vote: 3
Catherine Delahunty - Green list
Julie Anne Genter - Green list
Eugenie Sage - Green list
Did not respond*: 5
Jonathan Coleman - National Northcote
Bill English - National list
Lindsay Tisch - National Waikato
Annette King - Labour Rongotai
Maurice Williamson - National Pakuranga
*Some MPs are overseas