Valve Corporation, the owner of video game distributor Steam, is being sued in a class-action lawsuit for £656m for allegedly using its market dominance to overcharge 14m UK customers.

Steam is the largest platform selling PC games across the globe, and the lawsuit is claiming that Valve is using this platform to “rig the market” and shut down competition.

According to claimants, Valve’s terms and conditions requires games publishers to sign a ‘price parity’ obligation, which prevents video game titles from being sold at cheaper prices on different platforms.

Vicki Shotbolt, who is bring the case to the Competition Appeal Tribunal in London, says that this has allowed Steam to charge a 30% commission on games, and she claims UK consumers are largely fronting the bill on these extra costs for games and game-add ons.

“UK gamers spend billions every year and Valve has a stranglehold on the PC gaming market. Competition law is there to protect consumers and ensure that markets work properly,” Natasha Pearman, leading partner in the lawsuit which has been filed by Milberg London LLP, said.

According to VG Insights, Steam saw record-breaking sales last year, resulting in £7.1bn in global revenue, with 580m games sold.

The video game market is largely dominated by popular games, with the top ten bestselling games accounting for the majority of sales.

According to Osum, Steam dominates around 80% of the EU market share of video game distributors, showing is popularity. Its online platform is not console-dependent, meaning that users can purchase games for various platforms and consoles.