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.

Unions say the policy could lead to unsafe workplaces as new employees will be too afraid to raise concerns.

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 is expected to give details when he speaks at the National Party's mid-term conference in Auckland on Saturday.

Chief executive of the Employers' Chamber Peter Townsend said the trial had been an "outstanding success" with no problems.

"If you don't have it employers won't take the risk of employing new people," he told Radio New Zealand.

Having the chance to get to know the person and be sure they will fit removed the risk to hiring.

A survey of 400 employers found 48 fired someone in the trial period; "that could have been a good outcome for the employer and the employee, where it's simply a case where they don't fit, they're not getting on and they would be far better off to find employment somewhere else".

Green Party MP Keith Locke said the policy was a breach of National's pre-election industrial relations policy.

Labour leader Phil Goff told Radio New Zealand Mr Key was appeasing his "hard core, ideological supporters", there was no demand for the policy and sacked workers would be treated unfairly.

"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".

The Rail and Maritime Union said the 90-day policy raised safety concerns because new workers would not report concerns worried they would not be kept on. Restricting union access would compound that problem and make under-reporting of accidents more common.

The Association of Salaried Medical Specialist executive director Ian Powell said the policy would be terrible for recruitment as people would not want to risk changing jobs. Doctors who raised concerns about resources and support may be branded troublemakers and be sacked. "This is both unfair and stupid".

- NZPA