19 Sep 25. UK “too timid” in defending vulnerable undersea cables from attack, Committee finds.
Report: Undersea cables
The Government is “too timid” in defending its vulnerable undersea internet cables from attack, a cross-party Committee has found.
MPs and Peers on the Joint Committee on the National Security Strategy warn that the UK’s undersea internet cable network represents a strategic vulnerability in the event of hostilities. The report criticises the inadequacy of security preparations.
The report argues for “more muscular deterrence” measures, with punitive consequences for malicious damage. Recommendations include scaling up monitoring schemes, speedier data sharing with law enforcement, legal sanctions, and a greater focus on “direct physical interdiction and prosecution” of suspicious vessels and crew. The Committee suggests that “an assertive approach might yield some success”, while highlighting the risk of retaliation.
The Committee concludes that the cable industry offers “commendable” resilience against moderate damage, and there is “no imminent threat to the UK’s national connectivity”. But it also cautions against adopting industry’s business-as-usual views to determine risks to national security. It notes the challenge that Russian aggression can escalate much faster than UK resilience measures could be upgraded: “we can no longer rule out the possibility of UK infrastructure being targeted in a crisis. We are also not confident that the UK could prevent such attacks or recover within an acceptable time period”.
Undersea cables are a hidden but vital part of global internet infrastructure. Around 570 cables, usually run by private companies, carry 95-99% of the world’s intercontinental telecommunications data. There has been growing concern about malicious reconnaissance and sabotage, including a recent incident involving the Russian spy ship Yantar loitering over UK subsea infrastructure.
The UK is a global hub for internet traffic, and almost entirely reliant on subsea cables to transmit its data to the outside world. A small number of high-capacity cables are expected to carry a growing proportion of internet data, driven by large technology firms seeking supply routes for their services. The report highlights concerns that these trends are creating a small set of high-value targets.
There are particular vulnerabilities around the UK’s outlying islands, military cables and the financial sector. While sabotaging these links may not cause national disruption, it would be “costly, provocative and hard to prevent”. The Committee estimates the impacts of more extensive attacks would cause catastrophic disruption, including failures in payment systems and supply chains, degraded communications, overstretched emergency responses, and unexpected cascading issues as online authentication applications are disrupted.
The report calls for more robust resilience plans, particularly in the financial sector, and updated contingency planning scenarios to account for damage to onshore landing stations.
The Committee also recommends that the Government acquires a cable repair ship by 2030, to address the lack of genuinely sovereign repair capacity. This vessel would be leased to industry during peacetime but made available to Government in a crisis. The report calls on the Royal Navy establish a cadre of reservists and serving personnel to learn cable repair skills, to ensure cables could be repaired in a conflict scenario.
Matt Western, Chair of the Joint Committee on the National Security Strategy, said: “Undersea cables are the invisible backbone of the internet. Everything from everyday WhatsApp messages to financial transactions worth billions of dollars are carried through this network. The scale of the UK’s strategic reliance needs to be taken more seriously. While our national connectivity does not face immediate danger, we must prepare for the possibility that our cables can be threatened in the event of a security crisis. Putin has shown every sign of wanting to test the soft underbelly of the NATO alliance. Our cables are sufficiently vulnerable to make them a target. Competent and farsighted preparation is essential. The past 25 years show that unlikely events can happen with surprising speed and frequency. Unintended escalation is a particular concern given events in Ukraine. The Government must raise its gaze. Focusing on fishing accidents and low-level incidents is no longer good enough. We need stronger physical protections, better options to impose genuine costs for malicious activity, and more comprehensive recovery plans. It is conceivable that the UK’s national resilience will be tested in the coming years. We need to be ready.”
16 Sep 25. Joint Committee on the National Security Strategy. Joint Committee on the National Security Strategy to publish report on undersea cables. The Joint Committee on the National Security Strategy will publish the report of its inquiry into undersea cables at 00.01 on Friday 19th September 2025. Embargoed copies of the report will be available on Wednesday 17th September. If you are in receipt of this email you will automatically receive a copy.
The Committee has been considering the UK’s ability to defend its undersea internet infrastructure and national resilience in the event of protracted disruption. More details on the inquiry are available on the Committee’s website.