Unions are vowing to continue the fight against an employment law change passed by Parliament last night.
The 90-day trial period for new employees has been extended to all businesses.
Previously it was limited to those with 20 or fewer employees and the change was voted through 64-56 against strong opposition from Labour and the Greens.
Council of Trade Unions president Helen Kelly says there won't be any let up in the campaign against the 90-day law, which the Labour Party calls "fire at will" legislation.
"Unions are not sitting back in defeat at this moment," she said last night.
"We will continue to campaign against this government's attack on work rights and its continuing failure to take adequate action against unemployment."
Ms Kelly said the Government had chosen to listen only to business lobbies.
"There are 150,000 New Zealanders officially unemployed, yet the Government's response is to weaken everyone else's job security as though that was the root of the country's economic problems," she said.
"It seeks to weaken wage bargaining when our wages are falling further and further behind Australia's."
Labour Minister Kate Wilkinson said during the third reading debate on the bill the probation period had been a success.
"Rather than the sky falling in, as was hysterically proclaimed, employers of small and medium-sized businesses gained the confidence to hire new employees," she said.
"It is a fact that without the trial period, hundreds of New Zealand workers would not have the jobs they currently do have."
Ms Wilkinson said businesses didn't want to face a personal grievance if they hired someone who turned out to be unsuitable.
"They simply chose not to hire anyone. The 90-day trial has changed that."
Labour's Trevor Mallard said extending the trial period to all businesses was "just a continuation of the National Party's attacks on the rights of wage and salary earners and their conditions."
He said the law wasn't helping the economy and had been brought in for political reasons.
"It weakens the processes around job security, extends the range of reasons for dismissal, restricts substantially the right to appeal, and restricts the right to reinstatement," he said.