National could also continue its policy of directing its supporters to vote for United Future's Peter Dunne in Ohariu and the Act candidate in Epsom, while encouraging them to give their party vote to National.
Labour leader Andrew Little said that following discussions between the parties, both Labour and Greens had decided they would back themselves "with our own electoral commitments".
They had various reasons for running their own candidates in all the electorates, he said. The Greens did it to campaign for the party vote, and Labour always planned to compete in every electorate because it was one of the two big political parties, he said.
Withdrawing candidates altogether would have been a step further than the 2014 election, when the Greens made it clear to supporters that they should vote for a Labour candidate.
Green Party co-leader James Shaw said today a similar strategy could still be employed at this year's election: "Nothing is off the table."
However, if the Greens decided to pull a candidate from a marginal seat or direct their supporters to vote for a Labour candidate it would be on their own initiative, not as part of a formal arrangement with Labour.
Shaw said the Greens remained committed to running a candidate in all 71 electorates including all seven Maori seats for the first time.
He did not agree that running candidates in Maori seats would undermine Labour's chances given the joint approach by the Maori Party and Mana in those electorates.
In 2014, Davis won Te Tai Tokerau by just 743 votes over Harawira while the Maori Party candidate won 2579 votes.
Davis has said he is relaxed about the different contest this year because his profile is higher than three years ago.
Meanwhile, the Green Party's Auckland Central candidate Denise Roche is facing a challenge from political newcomer Chloe Swarbrick.
The party's nominations for the Auckland Central seat closed yesterday and Swarbrick and Roche are the only candidates to put their names forward.
Auckland Central is a key electorate for the Greens, who focus most of their energy on winning the party vote and received more votes than Labour in the seat in 2014.
Labour announced today that two relative unknowns, lawyer Helen White and educationalist Shanan Halbert, had put their hands up to replace Ardern as Labour's candidate in Auckland Central.
After narrowly losing to Kaye twice, Ardern is now running in the byelection for the safe Labour seat of Mt Albert.
Former Internet Party leader Laila Harre, who rejoined Labour last year, had said there was a remote possibility she would seek the Auckland Central nomination.
But she said today she was now more likely to play an organisational role within the party rather than run for Parliament.