The Council of Trade Unions says the Government's labour law reforms contradict its goal of increasing New Zealand's productivity.
The Transport and Industrial Relations Select Committee is hearing submissions on two bills to enact the changes.
The Employment Relations Amendment Bill extends the 90-day work trial for new employees to all employers and restricts access by union officials to the workplace.
The CTU says it will not create the jobs the Government suggests.
Secretary Peter Conway told the committee that productivity fell during the early 1990s under the Employment Contracts Act.
He said bad practices by employers will drive down wages and conditions, and hurt the economy.