The Government is rejecting accusations its proposed labour law changes will drive down wages and conditions.
Unions have denounced measures in the Employment Relations Amendment Bill introduced to Parliament last week.
At present unions and employers are required to keep negotiating collective agreements in good faith unless there is a genuine reason not to.
In the legislation, the Government is proposing that the requirement to conclude a collective agreement be removed.
The Labour and Green parties say provisions on collective bargaining will mean more employees will have to negotiate their own terms and conditions which will result in lower wages.
They say in a tight labour market employers can choose the person who will work for the lowest pay.
However the Government says the change is aimed at saving time and money when it's clear agreement can't be reached, and is not intended to lower wages.
Business New Zealand's chief executive Phil O'Reilly said the Opposition parties' objection is based on the assumption that employers don't want to enter collective agreements, whereas many are in fact happy to negotiate such arrangements.
"They see the advantages of that for workforces that are large and have a lot of undifferentiated work. So the suggestion that somehow employers hate collective bargaining and are simply wanting any excuse to walk away from it is ludicrous."
Other measures in the bill allow for partial pay reductions in cases of partial strike action, and an end to the requirement for workers to be covered by collective agreements for their first 30 days in a new job.