BT is today calling on Critical National Infrastructure (CNI) providers to move off the UK’s ageing copper landline network this year as becomes increasingly unstable and the fault rate increases.

The call comes as BT data reveals that 60% of CNI customers in the UK currently have no plan in place to start migrating off the legacy analogue network.

BT is now encouraging CNI providers to help safeguard essential public services and work with its experts to review their technology estate, test impacted devices and switch to alternative networks by the end of 2025.

The UK’s CNI providers include sectors such as healthcare, water, energy, emergency services, local and central government, and fire and security.

As the country’s outdated analogue Public Switched Telephone Network ( PSTN) reaches the end of its life, it is becoming increasingly prone to faults and difficult to maintain.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%.

The transition away from the PSTN is impacting a wide range of critical public systems.

Moving the UK from analogue to digital connectivity is recognised as a necessary step by Ofcom and Government as a once-in-a-generation, industry-wide programme to help future-proof communications for everyone. 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customers off almost 300,000 legacy business lines in 2024, its data shows many CNI providers are still relying on outdated analogue connectivity for mission-critical services.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 CNI 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.

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 organisations 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.

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. 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 Is 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.