BT Group warned of potential disruption to key public services in the UK because many providers of critical national infrastructure remain bound to its copper-based public switched telephone network (PSTN) and have no plans to upgrade to digital systems.

The operator stated its ageing PSTN is becoming unstable and more prone to failures as it approaches the end of its life. BT called for critical national infrastructure providers to begin preparing to switch to digital technologies, ideally by the year-end.

BT moved 300,000 business customers off legacy networks in 2024, but stated 60 per cent of critical national infrastructure outfits currently have no plans to transfer away from analogue networks.

The operator’s plea targets organisations in healthcare, utilities, emergency services, local and national government, and fire and security sectors.

It explained organisations must assess the impact of switching on water monitoring sensors; medical phone lines; alarms for fire, security and lifts; roadside emergency phones; public transport help points; and some older card payment machines.

BT noted the greatest progress in developing a digital transition strategy had been made by the energy sector, with the water industry next.

The clock is ticking on the PSTN, with BT’s goal to retire it by 31 January 2027.

BT Business CEO Bas Burger said it is “simply too risky to run the UK’s essential public services” on an “ageing copper landline network”.

The company sought to entice change by highlighting the “better stability, security and efficiency” of digital infrastructure, along with operational benefits.