Ofcom has launched investigations into BT and Three after two separate outages in the summer caused nationwide disruption and impacted calls to emergency services.

In July, BT reported a software issue to Ofcom which disrupted mobile phone services interconnected with the EE network.The outage prevented BT and EE customers from making or receiving mobile calls to other networks, including when trying to reach 999 emergency services.

Separately, Three notified the independent regulator of an incident that caused a disruption to mobile services across the UK on 25 June 2025, also impacting 999 calls.

The regulator stated that the investigations will aim to establish the facts surrounding these incidents and assess whether there are reasonable grounds to believe that BT and Three failed to comply with their regulatory obligations.

Ofcom explained that mobile operators are required to take appropriate and proportionate measures to identify and mitigate risks and prepare for any event that could compromise the availability, performance and functionality of their network or service.

“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,” Ofcom said.

Earlier this month, the regulator fined Virgin Media £23.8 million for putting vulnerable remote assistance customers at risk of harm during the migration of analogue landlines to digital.

The penalty comes after an investigation into whether the company met its obligations to treat vulnerable customers fairly during the migration, which took place in in November and December 2023, revealed “serious systemic failures”.

According to Ofcom, Virgin Media failed to correctly identify and record the status of telecare customers, who rely on tools such as personal alarms, resulting in significant gaps in the screening process.

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