Pike River family members joined about 100 protesters outside Parliament to oppose changes to workplace safety legislation they say could lead to more disasters.

Anna Osborne and Sonya Rockhouse, whose husband and son were among the 29 victims who died in the Pike River mine explosion, addressed the rally organised by the Council of Trade Unions on Tuesday.

Reversing 2015 reforms

Workplace Relations Minister Brooke van Velden is advancing an amendment bill that would undo portions of the 2015 Health and Safety at Work Act, legislation passed after the Pike River disaster.

Under the proposed changes, employers with fewer than 20 staff would not be legally required to manage safety risks deemed non-critical.

Osborne warned the changes would inevitably result in more harm. "This will undoubtedly lead to more injuries and people may take shortcuts where there is no requirements to comply with the laws that larger workplaces must adhere to," she said. "We have seen the consequences of ignoring health and safety, look at Pike River."

'We fought hard to toughen up these laws'

The Pike River families said they had spent years campaigning for stronger workplace protections after the 2010 disaster.

"Because of Pike we fought hard to toughen up these laws," Osborne said. "We devoted our time to try save the lives of workers in New Zealand to make sure Pike never happened again."

Rockhouse criticised van Velden for not engaging with the history behind the current legislation. "It is criminal that we have had to remind people of the dangers of stripping health and safety protections," she said. "For example, the New Zealand Minister for Worksafe admitted she hasn't read the Royal Commission report on Pike River yet, yet she feels equipped to suggest these unsafe and absurd amendments to health and safety laws."

Protesters delivered a petition carrying more than 15,000 signatures to New Zealand First leader Winston Peters.

Peters pledges to repeal law

Peters addressed the rally, saying coalition obligations compelled him to back the bill but vowing to prioritise its repeal should his party win office at the 2026 election.

"If we're given the chance at the 2026 election we're going to make getting rid of this legislation a priority," he said. "This bill won't last more than four and a months, it'll be dead on arrival."

Van Velden characterised Peters' remarks as last-minute political manoeuvring, saying New Zealand First had not raised particular objections during a meeting the previous month.

The minister said her bill incorporated recommendations from the Pike River inquiry that earlier governments had overlooked. She said the reforms would give industry a role in developing safety standards.

"We're asking for industry whether that's union or business to come to the table and actually help set standards for industry so there's guidance on what businesses need to do on the ground and also what workers need to do on the ground to keep each other safe," van Velden said.

Peters responded that his party had consistently raised objections, including at the earlier meeting.

Workplace death toll

Council of Trade Unions president Sandra Grey told the rally that hundreds of workers had died from illnesses caused by their workplaces, while more than 60 family members had been bereaved by workplace deaths in the past year.

The Green and Labour parties are opposing the bill, which was scheduled to pass its second reading on Wednesday before a final vote.