Nurses have told MPs that patient care could suffer if proposed changes to employment laws are allowed to go ahead.
A parliamentary select committee is hearing submissions on the Employment Relations Amendment Bill.
The legislation would allow employers to walk away from negotiations on a collective contract and in some cases it would ban strikes.
The New Zealand Nurses Organisation says it is opposed to all the proposed changes apart from the flexible working hours provision.
The union's industrial services manager, Cee Payne, told the committee its members have written 1000 personal submissions, which is unprecedented.
She says they are concerned about the impact of the changes on the relationships that have been established in the health sector with employers and other health workers over the last 10 years.
Ms Payne says members are worried the pressure on staff from the changes could have a negative effect on health outcomes for patients.
The Post Primary Teachers Association says the intent of the legislation is clearly to drive down wages and conditions - which it says will increase inequality and child poverty.
President Angela Roberts says the impact will be felt strongly in the classroom because when families are struggling, it's children that suffer.
The Public Service Association told MPs that the proposed changes attack workers' rights and will make it harder to get a fair deal through collective bargaining.