The Commerce Commission is taking a Wellington taxi company to the High Court for alleged price-fixing.
The market watchdog claimed that Hutt & City Taxis Limited breached the Commerce Act in September by reaching an agreement with two competing taxi firms to fix a minimum fare of $25 from Wellington Airport.
"It's alleged the fare was implemented through the distribution of stickers displaying the minimum charge to be placed on taxi vehicles," the commission said.
The conduct ceased in November, after which an investigation was launched, the commission said.
It also claimed the company engaged in anti-competitive behaviour with a third company.
The commission is seeking a declaration from the High Court that Hutt & City breached the Commerce Act, along with penalties and costs for the actions.
"Cartel conduct harms consumers by preventing businesses from competing to provide better quality services at better prices, and it harms other businesses which are trying to compete fairly," Commerce Commission chair Anna Rawlings said.
It had also sent warning letters to the company's four former directors and to a separate company, Kiwi Cabs, over its role in the conduct.
As the alleged breach occurred before cartel behaviour was made a criminal offence in April, the old laws would be applied.
If proven, the company could be fined up to $10 million, three times its commercial gain or 10 percent of its turnover per year, per breach.