TL;DR
Ofcom has launched formal investigations into BT and Three following nationwide mobile voice outages that at times prevented users from calling other networks and emergency services. The regulator will assess whether the operators breached licence obligations to manage availability and mitigate risks.
What happened
The UK telecoms regulator, Ofcom, has started formal inquiries into BT and Three after separate mobile voice failures this year left users unable to make calls, including to the 999 emergency number. BT informed Ofcom that a software fault on July 24 and 25 disrupted mobile calling across the EE network, stopping BT and EE customers from connecting calls to other networks or reaching emergency services. Three reported a June 25 incident that similarly affected voice services and access to emergency lines; that outage occurred a few weeks after Three completed a merger with Vodafone. Three described its disruption as being caused by an exceptional spike in traffic triggered by a third-party software configuration change and said it is cooperating with Ofcom. BT did not immediately comment to the publication that reported the regulator’s action. Ofcom will establish the facts and determine whether the operators failed to meet their licence duties to identify risks, prevent service failures and remedy adverse effects when incidents occur.
Why it matters
- Access to emergency services was impaired during the incidents, raising public-safety concerns.
- Ofcom’s investigations could lead to enforcement actions or fines if licence obligations were breached.
- The episodes highlight vulnerabilities in major UK networks and the need for robust risk controls.
- Recurring large-scale outages may erode customer trust and prompt tighter regulatory scrutiny.
Key facts
- Ofcom has opened formal investigations into BT and Three over mobile voice outages this year.
- BT reported a software issue on July 24 and 25 that affected mobile calling on the EE network nationwide and prevented calls to other networks and 999.
- Three reported a voice disruption on June 25 that also impacted access to emergency lines; this was reported weeks after its merger with Vodafone.
- Three said the June disruption followed an exceptional spike in network traffic caused by a third-party software configuration change and is cooperating with Ofcom.
- BT did not immediately respond to questions from the reporting outlet.
- Under their licences, mobile operators must take appropriate steps to identify and mitigate risks to network availability and to prevent or remedy adverse effects.
- Ofcom will assess whether there are reasonable grounds to believe BT and Three breached those obligations.
- The regulator previously fined BT £17.5 million in July 2024 for a 2023 999 outage and fined Three £1.9 million in an earlier case involving emergency access failures.
- Past enforcement suggests fines are a possible outcome if breaches are found, though any such penalties are not yet determined.
What to watch next
- Outcome of Ofcom’s investigations, including any enforcement actions or fines — not confirmed in the source.
- Any detailed technical findings and remediation plans published by BT or Three — not confirmed in the source.
- Whether operators announce compensation or support measures for affected customers — not confirmed in the source.
Quick glossary
- Ofcom: The UK communications regulator responsible for enforcing rules on broadcasters, telecoms, and postal services.
- 999: The UK emergency telephone number used to contact police, fire, ambulance and other emergency services.
- Network availability: A measure of a telecommunications network’s ability to provide service and handle user traffic without interruption.
- Licence obligations: Regulatory duties set out in an operator’s licence, including requirements to manage risks and maintain service continuity.
- Third-party software configuration change: An adjustment to software supplied or managed by an external vendor that can affect system behaviour if not correctly implemented.
Reader FAQ
Are BT and Three under formal investigation?
Yes. Ofcom has opened formal investigations into both operators over this year’s mobile voice outages.
What caused the outages?
BT reported a software issue on July 24–25; Three attributed its June 25 outage to an exceptional traffic spike tied to a third-party software configuration change.
Will Ofcom issue fines?
Past cases have resulted in fines, but whether fines will be imposed in these investigations is not confirmed in the source.
Did the Three–Vodafone merger cause the outage?
The source notes the June incident occurred weeks after Three merged with Vodafone, but any causal link is not confirmed in the source.
NETWORKS 26 Ofcom comes knocking after BT, Three mobile outages cut 999 access Watchdog reviews if failures breached availability rules after downtime left millions unable to make calls Carly Page…
Sources
- Ofcom comes knocking after BT, Three mobile outages cut 999 access
- Ofcom investigates BT and Three following mobile network …
- Ofcom investigates BT and Three for failing to connect 999 …
- Ofcom probes BT and Three after outages hit emergency …
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