Neelie Kroes warned repeat offenders would face tougher penalties
A group of plastics companies has been fined 173m euros ($260m; £156m) by the European Commission for price-fixing and organising a market-sharing cartel.
The case centres on information exchanged over heat stabilisers that are used in packaging, credit cards and bottles amongst other items.
The companies involved include Akzo, Ciba and Elf Aquitaine.
Competition Commissioner Neelie Kroes said companies must learn that "breaking the law does not pay".
She added that repeat offenders face stiffer penalties and that "elaborate precautions to cover their tracks did not prevent the Commission from revealing the full extent of their determined efforts to rip-off their customers".
Twenty-four businesses that belong to 10 different corporate groups are being punished.
The commission says the Swiss firm AC Treuhand provided its premises for monthly meetings to discuss details on prices and customer allocation.