Telecoms giant BT has today “urged” providers of Critical National Infrastructure (CNI) to “move off” the “outdated copper network” as it is becoming “increasingly unstable“. BT claims its own data shows that 60% of CNI customers in the UK currently have no plan in place to start migrating off the legacy analogue network.

Just for some context. Sites or networks designated as CNI are those facilities, systems, sites, information, people, networks and processes, necessary for a country to function and upon which daily life depends. It also includes some functions, sites and organisations which are not critical to the maintenance of essential services, but which need protection due to the potential danger to the public (e.g. civil nuclear and chemical sites).

NOTE: Energy supply, water supply, transportation, health, data centres and telecoms (e.g. broadband and mobile) are all considered CNI.

However, to be clear, BT’s call is more focused on the looming switch-off of the legacy Public Switched Telephone Network (PSTN) in favour of IP-based digital phone (VoIP etc.) services, rather than the much longer winded withdrawal of physical copper lines themselves that will take many years to complete. Openreach are withdrawing their old Wholesale Line Rental (WLR) products as part of this, while BT are retiring the related PSTN.

The big switch-off itself was last year delayed to 31st January 2027 in order to give internet service, phone providers, telecare operators and consumers more time to adapt (details). But the main focus of this delay was the 1.8 million people who use vital home telecare systems in the UK (e.g. elderly, disabled, and vulnerable people), which aren’t always compatible with the replacement VoIP / IP-based digital phone services. For everybody else, the deadline is still technically Dec 2025.

Suffice to say that BT are now pushing for key network and CNI providers to get off the PSTN before the deadline, not least due to its lack of support. This will help to stop the switch-off disrupting critical public systems, such as 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.

Ofcom’s recent Connected Nations report underlined the issues by highlighting that, in 2024, the number of significant PSTN resilience incidents reported increased sharply by 45% (here). Despite this, BT itself found that 60% of their CNI customers are yet to put a strategy in place for transitioning to digital networks.

However, 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. BT added that they moved customers off almost 300,000 legacy business lines in 2024, but many more have yet to follow.

Bas Burger, CEO of 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.”

As part of the national move away from the PSTN, it’s already no longer possible to sign up to legacy BT phone or broadband services. From 31st 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. But any technology still relying on the PSTN will stop working when the old network is retired.

The Government recently announced the PSTN Critical National Infrastructure Charter, which outlines the safeguards that Communication Providers (CPs) and Network Operators (NOs) must put in place during this change to the UK’s connectivity infrastructure. BT is thus urging these organisations to act now, and work with its team (or their existing ISP) to review their technology estates to identify any impacted devices, test whether these devices are compatible with alternative connectivity and make the switch in 2025.