Ofcom has launched investigations into BT and Three following outages in the summer that resulted in UK-wide disruption to mobile call services, including to emergency services.

Mobile operators are required to take appropriate and proportionate measures to identify and reduce the risks and prepare for the occurrence of anything that compromises the availability, performance or functionality of their network or service.

Providers must also take appropriate and proportionate measures to prevent adverse effects arising from any such compromises. Where there is an adverse effect on the network or service, the provider must take appropriate and proportionate measures to remedy or mitigate that effect.

Companies are legally obliged to report outages to Ofcom above certain thresholds.

BT has notified Ofcom of a software issue that resulted in a UK-wide disruption to mobile call services interconnecting to and from the EE network on 24 and 25 July 2025. This resulted in BT and EE customers being unable to make or receive mobile calls to other networks and emergency services.

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Separately, Three has notified Ofcom of an incident that resulted in a UK-wide disruption to call services on 25 June 2025, including customers’ ability to contact emergency services.

Ofcom’s investigations will seek to establish the facts surrounding these incidents and assess whether there are reasonable grounds to believe that BT and Three have failed to comply with their regulatory obligations.