Microsoft is facing a £1 billion legal action from UK businesses over claims it overcharged firms for access to products.

A claim filed to the Competition Appeal Tribunal alleges customers using rival cloud computing platforms to Microsoft’s own Azure were charged higher licensing fees to access its Windows Server.

It alleges that UK businesses and organisations are collectively owed more than £1 billion in compensation for being overcharged, and that Microsoft has used anti-competitive practices to try to force customers to move to its cloud computing services.

The claim has been filed by digital markets regulation and policy expert Dr Maria Luisa Stasi and law firm Scott+Scott, with all UK businesses who bought licences for Windows Server via rival cloud platforms such as Amazon’s AWS, Google Cloud Platform and Alibaba Cloud being represented in the “opt-out” collective action.

“Put simply, Microsoft is punishing UK businesses and organisations for using Google, Amazon and Alibaba for cloud computing by forcing them to pay more money for Windows Server,” Dr Stasi said.

“By doing so, Microsoft is trying to force customers into using its cloud computing service Azure and restricting competition in the sector.

“This lawsuit aims to challenge Microsoft’s anti-competitive behaviour, push them to reveal exactly how much businesses in the UK have been illegally penalised, and return the money to organisations that have been unfairly overcharged.”

James Hain-Cole, partner at Scott+Scott UK, said: ““Collective actions level the playing field and allow organisations to fight back against anti-competitive behaviour from some of the biggest companies in the world.

“Dr Stasi’s case against Microsoft aims to do exactly that. We are proud to support her efforts to secure compensation for the class and hold Microsoft to account for its conduct that affects businesses and organisations across the UK economy.”

Microsoft has been approached for comment.