The Royal Navy is reportedly mulling a drone flotilla to gather intel on Moscow's alleged "shadow fleet"

Britain is planning to launch a seaborne drone fleet to seize oil tankers it claims are linked to what it calls a Russian "shadow fleet," the Sunday Times has reported.

London banned the import of Russian crude and oil products in 2022, along with related maritime transportation, insurance, and financing, imposing sanctions on over 500 vessels.

Despite those measures, Moscow has shipped 550 million tonnes of oil legally through the English Channel with an estimated value of $326 billion, according to the outlet, which said the sanctions are "failing to bite." At the same time, Politico reported an estimated 40% of diesel-grade petroleum products the UK imported from India and Trkiye over four years originated from Russian oil.

The Royal Navy has drafted proposals for a command center for a remotely piloted flotilla of unmanned boats to police the North Sea. The drones are intended to gather evidence of "illicit activities" by tankers heading to and from Russian ports, which would form the basis for outright seizure of the vessels in the English Channel.

Under the UN Convention on the Law of the Sea, which guarantees freedom of navigation, Western powers lack a clear legal basis to enforce sanctions against cargo on the high seas.

Despite this, two tankers have been seized so far this year: the Marinera by the US with UK support in the North Atlantic, and the Grinch by France in the Mediterranean. British Defense Secretary John Healey confirmed afterwards that the two allies were coordinating to detain more vessels.

The Sunday Times noted, however, that the plan faces a significant financial hurdle, as holding seized tankers incurs high costs. To help offset this, London is reportedly considering selling the oil from impounded vessels.

READ MORE: Moscow condemns Ukrainian 'terrorist attacks' in Black Sea

Russian officials have consistently slammed tanker seizures a "blatant violation" of international maritime law. President Vladimir Putin last October called France's detention of a vessel in neutral waters "piracy." Foreign Ministry spokeswoman Maria Zakharova previously characterized piracy as "one of the English traditions," adding that historically pirates were forbidden to attack English ships but were allowed to plunder rival vessels.