Vladimir Putin is suspected of using Russian fishing boats to spy on Britain’s vital undersea cables, raising fresh fears over the UK’s security if war breaks out. More than 500 incidents in which Russian trawlers allegedly loitered above key communications cables or followed their routes across the seabed, The Telegraph reports. The newspaper analysed four and a half years of vessel-tracking data and identified 17 Russian ships that spent long periods moving slowly near cables linking Britain with Europe and the US.

The cables carry huge amounts of data and support services, including banking, mobile phones, hospitals and transport. Around £65billion of UK economic activity depends on subsea communications cables that carry data between Britain and the US. If the cables were damaged during a conflict, the disruption could seriously affect everyday life.

A NATO source told The Telegraph: “We’re absolutely aware of what Russian civilian fishing ships are up to and where…Some of these ships have never seen a single fish on their deck.”

A serving naval officer warned that the boats could potentially be equipped for secret underwater operations.

They told the newspaper: “If you put a sonar-equipped ROV 100 metres above a feature of interest, you can map it with millimetre precision.”

The findings come amid growing warnings about Russian activity around Britain’s critical infrastructure. The head of the Royal Navy, Gen Sir Gwyn Jenkins, has warned Russia could target undersea cables from “day one” of a conflict with NATO.

The Government is preparing tougher laws to protect the infrastructure, including proposed prison sentences of up to 14 years for intentionally damaging undersea cables. Ministers are also considering whether the maximum penalty should be life imprisonment.

The revelations come days after the Government launched its “Be Ready” campaign, urging households to keep enough essential supplies to manage for three days if a major emergency disrupts everyday services.

Read More: WW3 fears erupt as Putin sends fishing trawlers to spy on Britain