Britain urged to harden defenses after report warns undersea cables face catastrophic attack risk

Britain's network of undersea cables that connect the UK with the world is at risk of a 'catastrophic attack', MPs warned in a report released Sept. 18, 2025. The National Security Strategy Committee said the cables are vulnerable to sabotage in a crisis and that the United Kingdom is not confident it could prevent disruption to its communications and internet links. The cables, which run along the sea and ocean floors, form the backbone of modern data transfer and are largely controlled by private companies. The report argues the scale of the UK's strategic reliance on this network requires more urgent attention given the deteriorating security environment and growing NATO responsibilities.

The committee notes that more than 50 data-cable systems connect Britain to the world, and that all of them face potential exploitation if a conflict escalates. It points to Russian ships surveying these networks and warns that they could be attacked at a time of war. The report stresses that the UK's defenses against sabotage and physical damage to subsea links are not robust enough to guarantee continuity of service in a crisis.

MPs say security preparations for the network are 'inadequate' and urge faster repairs, increased military exercises to protect cables, tougher penalties for wrongdoing, and new integrated monitoring and alert systems to improve early warning and vessel interception. The report also notes that the world's data-cable network comprises roughly 570 cables (plus a further 80 planned) that carry between 95% and 99% of intercontinental telecommunications data, with satellites handling only about 5% of the capacity. The UK, as an island nation, is almost entirely reliant on subsea cables to transmit data and serves as a major onward transit route for transatlantic links.

The cables carry the data that power the economy, everyday communications and critical services, the committee notes, warning that the trend toward high-capacity, few high-value targets could concentrate risk in a small number of chokepoints. The report calls for speedier repairs of damaged or degraded cables, more military exercises to practice protecting cales, legal changes to introduce tougher penalties for malicious damage, and new integrated monitoring and alert systems to improve early warning and vessel interception. It adds that, while there is no immediate danger, the deteriorating security environment requires a higher level of readiness as state actors, including Russia and China, could exploit vulnerabilities in times of crisis.

Context for the warning comes as Russia has been accused of testing NATO resilience in recent weeks, including incursions into NATO-adjacent airspace and intensified activity near European borders. The committee argues that Putin has shown an interest in probing the soft underbelly of Western alliance structures, and that the UK’s offshore cables must be defended accordingly. It also emphasizes that the country cannot rule out the possibility of infrastructure targeting in a crisis and that the government should elevate its gaze to account for strategic dependencies that stretch across oceans and continents.

The report underscores the fundamental role of subsea cables in global connectivity. Subsea cables are typically operated by private companies and carry everything from financial transactions worth trillions to everyday messaging. They connect to national data infrastructure through landing stations along coastlines, feeding data into terrestrial networks. In the UK, this network underpins both daily communications and critical services, from banking systems to emergency services, and the disruption of even a single link could cascade across international supply chains. As such, lawmakers say it is vital to bolster protections, align legal regimes, and ensure rapid restoration capabilities to minimize downtime in a crisis. The government is expected to respond to the committee's recommendations in the coming months as it weighs the balance between public protection and private sector resilience in this essential digital lifeline.