Changes in style are expected at the Commerce Commission as a new leader takes control.
Current chair Paula Rebstock is to step down at the end of this month after serving more five and a half years in the role.
Last month, the commission announced it would be more vigilant than ever about anti-competitive behaviour as the economic recession tightens.
Less than three weeks later, Ms Rebstock has stepped down. Former deputy chair Mark Berry is to be her replacement.
The head of the competition team at Minter Ellison Rudd Watts, Andrew Matthews, says the agency will likely slow its expansion of regulatory powers.
The comission says Ms Rebstock is not yet ready to give interviews on either her time at the commission or her resignation.