Ofgem has fined Engie Global Markets £2.1 million after one of the firm's UK traders manipulated wholesale gas prices to increase trading profits.
The trader acting on the French energy company's behalf engaged in 'spoofing' - placing fake bids to influence the market price then buying or selling at a higher or lower price.
The industry watchdog was tipped off in November 2016 and an investigation under its REMIT rules found EGM had tried to manipulate prices through a month-ahead natural gas contract between June and August 2016.
Ofgem said EGM failed to take adequate measures to prevent or detect the breach. However, since August 2016, it had taken measures to help prevent a repeat and was granted a 30% discount on a potential £3 million penalty.
Ofgem chief executive Dermot Nolan said: "This investigation demonstrates Ofgem's commitment to monitoring wholesale energy markets in Great Britain and ensuring their integrity on behalf of consumers.
"Ofgem's enforcement action under REMIT sends a strong signal to all energy market participants that we have the powers to tackle market manipulation wherever we find it - and are ready to use them."
