Facing a series of questions on the impact on national security and public services of the shutdown of ISDN and PSTN systems, minister Chris Bryant has revealed mitigations are underway
Government is “actively monitoring the progress of mitigation plans” being developed by departments that continue to rely on the PSTN and ISDN national telecoms infrastructure that will be switched off in little more than two years.
PSTN and ISDN – otherwise respectively known as the Public Switched Telephone Network and Integrated Services Digital Network – are both operated by BT, which intends to close the systems permanently by 31 January 2027. This shutdown date has been pushed back by 13 months, following a decision taken by BT earlier this year to give users more time to switch to internet protocol-based voice alternatives.
In 2026, the two networks will each celebrate a significant birthday: copper cable-based PSTN will pass its 150th anniversary, while the digital ISDN upgrade will mark 40 years in operation.
As many as two million lines remains connected to the outgoing infrastructure, and government has faced various parliamentary questions in recent weeks regarding the switchover process and the security implications – particularly for public services.
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The minister for data protection and telecoms, Chris Bryant, said that the Department for Science, Innovation and Technology “chairs a quarterly cross-government group on this issue, to which all government departments are invited”. The meeting helps DSIT in its work to track any government bodies that continue to rely on ISDN or PSTN – and the efforts being undertaken to enable a digital switchover.
“The group allows for discussion around plans and progress, and the opportunity to raise any concerns around the retirement of these legacy networks,” Bryant said. “Where dependencies have been identified, the department is actively monitoring the progress of mitigation plans and engaging with industry on removing obstacles to migrating off legacy networks.”
The minister also revealed that his department strives to engage with the Home Office, in particular, in an effort “to identify and mitigate risks associated with the PSTN switchover, including risks posed to the emergency services”.
Bryant added: “The department also supports the 999 / 112 Liaison Committee chaired by the emergency services, which coordinates and manages all risks and issues related to 999 and ensures efficient handling of emergency calls between the public, call handling agents, and emergency authorities.”
This consideration of the possible impact on emergency services is supplemented by a wider effort in which “since the general election, I have worked with other departments and industry in an effort to ensure that the industry’s necessary retirement of the PSTN does not compromise national security, and that vulnerable people and others retain connectivity during emergencies”, according to Bryant.
The minister’s comments were made in response to written parliamentary questions from Liberal Democrat MP Richard Foord, and Conservative MP – and former data minister – Sir John Whittingdale.
