BT is calling on the U.K.’s critical national infrastructure (CNI) providers – including sectors such as healthcare, water, energy, emergency services, local and central government, and fire & security – to move away from the outdated analogue copper landline network by the end of December 2025.

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 highlights that in 2024, the number of significant PSTN resilience incidents reported increased sharply by 45 percent.

The transition away from the PSTN is impacting various 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.

“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landline network becoming increasingly fragile, it’s simply too risky to run the UK’s essential public services on outdated networks,” Bas Burger, CEO – Business at BT, said in a media statement. “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.”

Burger urged 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.”

Moving the UK from analogue to digital connectivity is a once-in-a-generation, industry-wide programme to help future-proof communications for everyone. 

Recognised as a necessary step by Ofcom and Government, it’s an investment in more stable, secure and efficient connectivity. 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customers off almost 300,000 legacy business lines in 2024, its data shows many CNI providers are still relying on outdated analogue connectivity for mission-critical services.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 is urging these organizations 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, and futureproof their operations.

New BT data highlights the progress still to be made across CNI sectors to harness the benefits of digital connectivity. As of December 2024, 60% 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% of BT customers in the energy industry and 64% 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 organizations with CNI services that currently rely on the legacy network, the Government recently announced the PSTN Critical National Infrastructure Charter, which outlines the safeguards that communication providers (CPs) and network operators (NOs) 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, with no business left behind.

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. Full-fibre broadband connectivity can deliver speeds that are up to ten times faster than copper-based connections.

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 Dec. 31, 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.