The Dairy Workers Union says removing the obligation on workers and employers to reach agreement on collective contracts doesn't make sense, as the whole point of bargaining is to get agreement.
Parliament's Transport and Industrial Relations Committee held a hearing on Thursday on legislation to amend the Employment Relations Act.
One change would remove the obligation on workers and employers to reach agreement on collective contracts.
The union's assistant secretary Angus McConnell says not having to conclude agreements would result in employers putting take-it-or leave it deals to unions.
"When you take away the obligation to conclude bargaining, you actually give those people who don't want to bargain a free ticket out of bargaining."
Mr McConnell says if there is no obligation to conclude bargaining there will be no obligation to start it.