The government's not ruling out further labour law changes - after the biggest shake-up in a decade passed through Parliament last night.

The changes mean employers won't be required to conclude collective bargaining, and will be able to negotiate to remove or alter breaks - and can dock pay from employees on a partial strike.

The amendments follow National bringing in the 90-day trial law - and now John Key's been asked, what next.

"Well we have a new minister, so there's always the potential for us to consider particular issues.

"I can't identify any at the moment."

Nurses Organisation spokeswoman Cee Payne says nurses are seriously concerned - and not just for themselves.

She says removing meal breaks and weakening real pay growth can't be good for the health of Kiwis.

"It's more difficult for them to be able to afford those things that they need to actually maintain the health of themselves and their families."

Payne says there wasn't anything wrong with the existing law.

Labour's Andrew Little says his biggest concern is the ability to remove tea breaks.

"It might be retail workers, so shop assistants, it could be some factory workers.

"The people I worry about most are those who are in service-type jobs where you need a break because you're on your feet or you're dealing with customers a lot and if you don't get a break you lose your edge."

Meanwhile, the amended employment law is seeing unions spit chips.

Council of Trade Unions president Helen Kelly says the law is an unprecedented undermining of workers rights.

"It is a disaster. You have to ask what sort of government does that to its population."

Kelly says it puts New Zealand at the extreme end of labour market deregulation.

However, Minister Michael Woodhouse maintains the law is about flexibility - and says Labour's misconstrued its impact.

"What angers me about the tub-thumping rhetoric by the cloth cap wearers in the opposition is that their irrational and incorrect description of the flexibility in the arbitrary removal of tea breaks has created a climate of fear."

National maintains the law is about flexibility - not removing tea breaks.