BT has called on the UK’s Critical National Infrastructure (CNI) providers to move away from the outdated analogue copper landline network by the end of December 2025.
CNI providers include sectors such as healthcare, water, energy, emergency services, local and central government, and fire and security.
As the country’s historic Public Switched Telephone Network (or PSTN) reaches the end of its life, it is becoming increasingly prone to faults and difficult to maintain. Ofcom’s recent Connected Nations report highlighted that, in 2024, the number of significant PSTN resilience incidents reported increased sharply by 45 per cent.
The transition away from the PSTN is impacting a wide range of critical public systems. This could include water monitoring sensors, phone lines for doctors and pharmacies, fire and burglar alarms, lift alarms, emergency phone lines by roads, help points at train stations, and some older card payment machines.
However, while BT moved customers off almost 300,000 legacy business lines in 2024, its data shows many CNI providers are still relying on outdated analogue connectivity for mission-critical services.
BT has urged these organisations to act now, and work with its team of specialists to review their technology estates to identify any impacted devices, test whether these devices are compatible with alternative connectivity and make the switch to more reliable digital networks in 2025. This will help customers mitigate the growing risks of communication disruptions.
New BT data highlights the progress still to be made across CNI sectors to benefit from digital connectivity. As of December 2024, 60 per cent of BT CNI customers are yet to put a strategy in place for transitioning to digital networks. However, significant progress is being made in key sectors: 80 per cent of BT customers in the energy industry and 64 per cent in the water industry have a plan in place or are advanced in their migration journeys, demonstrating strong momentum towards a more reliable and future-ready digital infrastructure.
The UK’s PSTN is set to be retired by the end of January 2027. To support organisations with CNI services that rely on the legacy network, government recently announced the PSTN Critical National Infrastructure Charter, which outlines the safeguards that communication providers and network operators will put in place during this change to the UK’s connectivity infrastructure. BT is one of the signatories to the charter, and has hailed it as a major milestone to mark the urgency of moving away from outdated infrastructure.
Bas Burger, CEO – business at BT, said, “With the ageing copper landline network becoming increasingly fragile, it’s simply too risky to run the UK’s essential public services on outdated networks. BT is committed to moving these services onto future-proofed modern connectivity well ahead of the closure of the analogue copper network – but we can’t do it alone.
“We're urging all Critical National Infrastructure providers to act now to help protect their services and reap the long-term benefits of going digital. Waiting until the analogue switch-off is too late. We’re working with customers to review their technology estate, test their critical devices and switch to more reliable connectivity by the end of 2025.”
The business benefits of switching from analogue copper to digital networks include better stability, security and efficiency – as well as other operational benefits. For example, digital landlines enable businesses to make and receive calls from one number via multiple devices and offer improved scam protection.
As part of the national move away from the PSTN, it’s no longer possible to sign up to legacy BT phone or broadband services. From 31 December 2025, any existing PSTN-connected business services may change in preparation for the full retirement of the network by the end of January 2027. Any technology still relying on the PSTN will stop working when the network is retired.