The Commerce Commission has issued an official warning to a seller on TradeMe for trying to fix prices with another seller.
The commission began investigations in September after a complaint that the seller - Ernie Travers of Massey in Auckland - emailed a competitor, suggesting they agree to sell LED bike lights at a set price.
Enforcement general manager Kate Morrison says Mr Travers denies sending the email, but could not satisfactorily explain who had sent the message.
Ms Morrison says price-fixing means consumers are likely to pay more than they otherwise would in a competitive market, and people who are selling on-line must be mindful of the Commerce Act.
She says any attempt to lessen competition will be viewed seriously, no matter what the forum.