The Bill contains the controversial 90-day probation period for new employees in workplaces which employ fewer than 20 workers.
The Otago Daily Times reported on Tuesday that a showdown was looming between National and the Maori Party on the issue, but Maori Party employment relations spokesman Hone Harawira played down the issue, saying it was a reflection of an "honest relationship" with National.
The Maori Party had a confidence and supply agreement with National but was free to make its own decisions on other legislation going before the House.
The party would vote against the legislation rather than abstain, he said in an interview.
However, National, Act New Zealand and United Future still have the votes to get the legislation through before Christmas.
Maori Party leader Pita Sharples met Prime Minister John Key to tell him before the decision was made public.
Mr Harawira said the Bill was an opportunity for the party to have the open relationship enhanced by speaking its mind.
The party opposed the Bill when it was introduced by National MP Wayne Mapp in 2006.
Apart from two cosmetic changes, it was the same legislation and there was no evidence the Maori Party should support it.
The legislation disadvantaged workers generally, not only Maori, he said.
"Lower pay rates for Maori workers across all industries indicate the extent of institutional racism that this Bill may unintentionally exacerbate, especially if the forecast recession increases unemployment," Mr Harawira said.
The Maori Party came in for a pasting in Parliament yesterday as senior Labour MPs took every opportunity to criticise the five MPs for supporting the tax cuts legislation.
Asked how he reacted to the comments made by Labour MP Trevor Mallard, Mr Harawira said he would "like to kill him", but that Mr Mallard had a point to make and every right to raise the issues he had.
Mr Harawira agreed with some of Mr Mallard's points, but he had not been in the House when the comments were made.
The Maori Party had not had a chance to go back to its voters yet because of the short time Parliament had been assembled, but Mr Harawira said the MPs were "comfortable" with where they were going.
The party would deal with the Bills as they were introduced.
Dr Sharples said the Maori Party's policy for workers was to support, uphold and extend their rights, particularly to make workplaces and work legislation more worker and family friendly.
"We have no evidence offered with this Bill that probationary periods provide gains for new, inexperienced or marginalised employees as claimed."
This was a situation where the Maori Party and the National Party disagreed on policy and the Maori Party had decided to oppose the Bill as provided for in its confidence and supply agreement, he said.
Labour Minister Kate Wilkinson responded to union concerns about the legislation by saying the Government had come up with a "gentler Bill" than the one introduced in 2006.
The legislation was not on the list National said it would pass in its first 100 days in power.
