Labour MP Trevor Mallard says today is a sad day in the country's employment relations history as the Government's controversial 90-day probation for new employees begins.
Mr Mallard said the legislation was "the latest chapter in (Prime Minister) John Key's short-sighted attempt to address the economic downturn".
"New Zealanders should not be fooled. National's attempt to try and sell this as a way to boost employment opportunities with small to medium sized businesses is a sham," he said.
The 90-day clause would make it far more difficult for small to medium businesses to attract skilled staff when they most needed them, he said.
The legislation, passed by Parliament in December, was opposed by Labour, the Greens, the Maori Party and trade unions.
It gives businesses with fewer than 20 workers the right to sack a new employee during the probation period without risking a personal grievance case.
But Labour Minister Kate Wilkinson said earlier this week it would be "a real boost" for people on the margins of the workforce who needed an employer to give them a chance in a new job.
"In the current economic climate this will encourage small businesses to give a prospective employee a go without fear of costly and protracted legal proceedings if the relationship doesn't work out," she said. "It must be remembered that a trial period is voluntary and can only be implemented if both the prospective employee and employer agree to it in writing."
Ms Wilkinson said it related only to personal grievances on the grounds of unjustified dismissal.
Other rights were retained so employees were still protected against discrimination, sexual and racial harassment, duress or unjustified action by an employer.
All the new provisions were fiercely debated in Parliament.
Opposition parties said the 90-day probation was a vicious assault on workers' rights and would give unscrupulous employers the ability to get rid of anyone for any reason without explanation.
MPs said young people, and particularly immigrants, would be exploited because many of them would be prepared to sign almost anything to get a job.
The Government - which made an unsuccessful bid to get the law through by using a member's bill while National was in opposition - was determined to pass it and used its majority, with the ACT Party, to vote it in.
NZPA