Key Points:

The Government is facing an outcry from unions and its opponents over plans to "ram through" a 90-day probation period for new workers before Christmas.

Prime Minister John Key today confirmed his plans to pass the controversial legislation - which will give businesses with fewer than 20 employees the right to instantly sack new staff - through all its stages before Christmas.

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.

The decision today prompted howls of outrage from Labour and the Greens which said it was undemocratic and arrogant.

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 legislation went before a select committee in the last Parliament in the form of a private member's bill introduced by National MP Wayne Mapp.

The bill was subsequently defeated.

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

Mr 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".

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

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

The legislation could provide an early litmus test for National's relationship with its support partner the Maori Party, which helped defeat the legislation in the previous Parliament.

Labour and the Greens called for it to stand by that position and to also vote against the Government's urgency motion.

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

But Maori Party co-leader Tariana Turia said the party was yet to see the legislation. It would consider its stance once it received it.

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.