Salesforce and its workplace messaging subsidiary Slack have launched proceedings against Microsoft before London’s High Court, alleging that Microsoft engaged in anticompetitive practices in relation to the bundling of its Teams collaboration platform.(Reuters)
The claim was filed on 23 April 2026 by Slack Technologies LLC and related entities. According to a spokesperson for Slack, the lawsuit alleges that Microsoft harmed competition by tying and bundling Teams with its broader Office software suite in a manner that restricted customer choice and disadvantaged rival workplace communication providers.
Microsoft has rejected the allegations, stating that the claim lacks merit. A spokesperson for the company said Slack’s slower growth relative to competitors such as Teams and Zoom reflected product shortcomings rather than anticompetitive conduct.
The UK litigation follows Slack’s earlier 2020 complaint to the European Commission, in which it accused Microsoft of leveraging its dominance in productivity software by bundling Teams with Office. That investigation concluded last year with Microsoft avoiding a formal infringement decision and potential fine after offering commitments to the Commission, including reduced pricing for Office packages sold without Teams.
The new lawsuit signals that private enforcement efforts are continuing notwithstanding the European settlement and could expose Microsoft to damages claims relating to the alleged foreclosure effects of its bundling strategy.
The filing also comes amid increasing litigation pressure on Microsoft in the UK. Earlier this week, London’s Competition Appeal Tribunal certified a separate collective action alleging that Microsoft overcharged British businesses for the use of Windows Server software on rival cloud infrastructure providers. Microsoft also disputes those allegations.
The Slack claim adds to the growing use of UK courts as a forum for follow-on and standalone competition damages actions involving global technology platforms.
