Key Points:

The Maori Party will today mull over whether to support the new Government's bill to set up a 90-day probation period for new workers.

The party's votes are not crucial to passing the legislation, which the government intends to do by Christmas.

However there is considerable interest in how the party will treat the first potential conflict with the government since it went into a support arrangement with National after the election.

Previously the 90-day proposal was contained in National MP Wayne Mapp's bill, which was defeated in the previous Government.

The Maori Party split its vote on the first reading, with Hone Harawira opposing and the other three MPs backing the bill, but subsequently the party made a policy decision to oppose it.

The new bill has caused an outcry from unions and the Green and Labour parties urged the Maori Party to maintain its policy and oppose it.

The bill would give businesses with fewer than 20 employees the right to instantly sack new staff.

The surprise move to pass the law under urgency will mean the public and groups such as unions won't have an opportunity to make submissions on the bill.

Unions said the change, which gives bosses a 90-day grace period to dismiss new workers without exposing themselves to claims of unjustified dismissal, would strip about 100,000 workers at any one time of a basic employment right.

But Labour Minister Kate Wilkinson said the public had already had a chance to give its views when the Mapp bill was considered.

Ms Wilkinson said the Government had taken several concerns on board and come up with a "gentler" bill.

Key changes included:

* barring employers from using the law to keep staff permanently casual by sacking them within 90 days then rehiring them;

* removing the benefit stand down period for those "let go" after the 90-day period;

* making mediation available for employers and staff who experience problems;

* making it clearer that workers will still have the right to lodge personal grievance claims on the basis of sexual harassment or discrimination.

The legislation was not on the list of legislation National said it would pass in its first 100 days in government.

Prime Minister John Key said it had campaigned hard on the issue and it was important to get the "growth enhancing" move in place, when New Zealand was facing job losses.

"This will assist the small to medium to medium enterprise sector to take on employees and to take them on rapidly," Mr Key said.

Labour leader Phil Goff said the public had been blindsided and should have a right to have their say on a law that removed basic rights.

"This piece of legislation which takes away those rights is going to be rammed through Parliament with no opportunity for public input," he said.

"That really is an outrageous act of arrogance and bodes badly for the future of this government that they are prepared to do so."

Mr Goff said the move would undermine workers' sense of security at a time when unemployment was rising.

He said it undercut Mr Key's rhetoric around providing security for workers in tough economic times.

Council of Trade Unions president Helen Kelly said the move to fast-track the law without giving the public a say was a "huge breach of good faith".

Unions would be campaigning hard against it.

Green Party MP Sue Bradford said the move to pass the "fire-at-will" bill under urgency was a "disgraceful attack on workers' rights".

"After all, Maori workers are among those most affected by unemployment and job mobility," Ms Bradford said.

She said the Maori Party should not only oppose the bill but also National's move to pass it under urgency.

Mr Key said their were protections for employees from unethical bosses.

Business New Zealand chief executive Phil O'Reilly said most other developed countries had probationary periods and congratulated the Government on moving quickly to address a key problem facing small businesses.