Even before it becomes law, the new 90-day trial period has sparked noisy protests.
A march is underway in central Auckland against the measure, which allows businesses with fewer than 20 staff to fire people in their first 90 days of employment. Unions are calling it the "fire at will law."
In Christchurch, a group calling itself The Workers Rights Campaign has picketed National MP Nicola Wagner's office.
They plan to take their objections directly to the premises of employers making use of the law to sack people unfairly.