Shares of Mercury (NZE:MCY, ASX:MCY) fell past 2% in recent trading on the New Zealand bourse on Tuesday, while those of Contact Energy (NZE:CEN, ASX:CEN) inched down less than 1% after New Zealand Energy Minister Simon Watts said in a Tuesday statement that the government had agreed to amend the Electricity Industry Act to strengthen the role of the Electricity Authority, which regulates the electricity market in the country.

Shares of Meridian Energy (NZE:MEL, ASX:MEZ) were up nearly 1%, while those of Genesis Energy (NZE:GNE, ASX:GNE) were flat.

The changes will boost the ability of the regulator to update rules and monitor the market and introduce instant infringement fines of up to NZ$2,000 for minor repeated breaches. They will also raise the penalties for serious breaches to up to NZ$10 million or three times the commercial gain or 10% of a company's turnover.

The infringement system will be put in place starting this year and the higher fines in 2027.