The Labour Party says it will repeal any moves by the Government to widen the 90-day trial scheme under which workers can be fired without comeback and to reduce union access to workplaces.
At the moment the 90-day scheme applies to employment in businesses with fewer than 20 staff and the Government has been looking at expanding to firms with 50 employees, but it appears set to be extended to all companies, regardless of size.
Prime Minister John Key said on One News that the results of the changed law had been "stunning" and meant many more New Zealanders had landed jobs.
Under the current law newly hired workers can be let go within the first three months and cannot take a personal grievance in reaction to their dismissal.
Mr Key apparently first unveiled the broadened scheme when he met business leaders yesterday.
He is expected to give details when he speaks at the National Party's mid-term conference in Auckland on Saturday.
Labour leader Phil Goff told Radio New Zealand Mr Key was appeasing his "hard core, ideological supporters", there was no demand for it and it was unfair.
Under the policy people could be sacked unfairly and have no right seek a personal grievance.
"This is about workers' job security, the right to protect their livelihood against unfair dismissal. These things are being taken away."
While most employers were good labour laws were there to protect against the bad ones. Those same bad employers would abuse the change to require unions get permission to enter workplaces.
"A bad employer is going to use that new law to prevent any worker having access to the union on the job site."
CTU spokeswoman Helen Kelly called the lack of right to appeal dismissal "disgraceful".
She said the CTU had represented a number of young workers who'd lost their jobs and it "has been a simply devastating experience",
She added it was believed upcoming law changes would also restrict union access to worksites, which she said was a throw-back to the bad old days of the Employment Contracts Act.