The Greens are bringing in more money to the party's coffers than their Labour allies, Electoral Commission documents show.

Donations and loan returns for the past calendar year show the Greens have a lot more in the bank, receiving more than $860,000.

Labour, on the other hand, have received $564,000, but leader Andrew Little believes his party is better prepared for the election campaign - more so than any other campaign he's been involved in.

"The average donation to the Labour Party is about $37 - that's how we campaign, those are the people that sustain Labour and give us and our campaign life, so I'm very pleased with that," Little said.

The Labour Party is holding its election year congress this weekend, which will see some 500 Party staffers, candidates and their campaign teams descend on Te Papa in Wellington.

Little will address the party faithful on Sunday, and has hinted at policies that might attempt to level the playing field so the rules are fair for younger couples, who're working hard to scrape together enough to own a home.

"First home buyers have not only got to save for a deposit, which in some cases can be up to two hundred thousand dollars if you're trying to buy in Auckland, and competing with a whole bunch others," Little pointed out.

Deputy leader Jacinda Ardern is also due to make a policy announcement in her speech, but is giving very little away about its content in advance.

"It's complementary to the some of things we've been placing a lot of emphasis on in recent times, and it's something that I feel quite strongly about, and have been involved with over a couple of different portfolios," she said. "It's something I have a personal passion for."

Ardern has maintained a consistently strong stance on issues around child poverty, and has raised concerns about the abuse of children in state care.

According to a Roy Morgan poll in late April, a potential Labour/Greens alliance has 43 per cent support. Labour's polling remained unchanged at 29.5 per cent, while support for the Greens fell 1.5 per cent to 13 per cent.

The ruling National Party remain steady at 43 per cent.