Union secretary Laila Harre told delegates the Greens and the Maori Party had been "our strongest backers" on key issues such as ending lower pay for young people and keeping shops closed at Easter, with Labour "a very close second" on both issues.
In a closed session with the MPs afterwards, she said the only way to prevent a National-led Government, based on an average of recent polls, was for the Maori Party to win all seven Maori seats, creating an "overhang" above the 120 MPs elected through proportional representation.
But it would then be critical for the Maori Party to use its seats to keep Labour in power.
"That message came through very clearly from our delegates in the questions and discussions after [the MPs] spoke," Ms Harre said.
"I think all three parties, certainly the representatives who were there, seemed to us to be very keen, if the cards were dealt to them by the electorate, to do that."
With Labour Cabinet minister Trevor Mallard on his left and Green co-leader Russel Norman to his right, Mr Harawira told delegates that many Maori wanted that outcome.
"I know a lot of my relations would dearly love to see me in a relationship with Trevor over here and Russel over here," he said.
Mr Mallard interjected: "What does your mum say, Hone?"
Mr Harawira replied: "My mum said, 'Do exactly that, Hone'. It's a tough one for us, Labour, because when you have been on the bottom for so long and you get an opportunity to make effective change, albeit small, you are going to go with whatever gives you the opportunity to make that change.
"I'd love the opportunity for the Maori Party to be in that position to effect change for Maori. I would personally like to see that change in an environment where workers' rights and workers' aspirations will continue to be well protected."
Mr Harawira's mother, veteran activist Titewhai Harawira, could not be contacted last night.
But Mr Harawira said later he had deliberately avoided saying which way the Maori Party would go because that decision would be taken only after the rest of the country had voted.
The Maori Party had voted with the Greens 80 per cent of the time, with Labour 60 per cent and with National on only 25 per cent of the issues.
The party had opposed the free trade deal with China because "at the level where the great majority of Maori exist, which is the working class and the beneficiaries, they are going to get hit seriously".
With 27 per cent of Maori children growing up in poverty, the party wanted to get a better deal by abolishing tax on incomes under $25,000, taking GST off food and raising the minimum wage to $15 an hour.
But he said the party could not commit itself in advance to Labour because "if Maori wanted just Labour, we would never have got into Parliament".
"We are actually in Parliament because Labour betrayed our people through the theft of our foreshore and seabed," he said.
"We know that Maori people historically have traditionally been Labour.
"We respect that. But all we would ask of anyone is that they give us the opportunity to do the best deal possible for Maori."
