British prime minister Keir Starmer will allow his country’s military to board ‘shadow fleet’ vessels transiting UK waters as the UK steps up its pressure on Putin, according to a Wednesday press release from his office.

The prime minister has agreed that the UK armed forces and law enforcement officers will now be able to interdict vessels that have been sanctioned by the UK and are transiting through UK waters.

It follows the Royal Navy supporting allies with the monitoring and tracking of several ‘shadow fleet’ ships to enable interdiction in European and Mediterranean waters in recent weeks.

A number of JEF allies, including Finland, Sweden and Estonia, have carried out recent operations against suspected illegal ‘shadow fleet’ vessels in the Baltic, closing off critical maritime routes to stop their operation.

The announcement coincides with Starmer’s participation in the joint expeditionary force summit in Helsinki, where regional security and responses to Russia were discussed.

The press release from Downing Street notes that ships traveling through the Arctic and high north can directly threaten important “lifelines” like the sea lines of communication that connect the US to Europe.

The release said military and law enforcement specialists have been put through their paces in preparation for a number of scenarios in recent weeks, including boarding vessels that don’t surrender, are armed, or use high tech pervasive surveillance to evade capture.

“Each target ship will be individually considered by law enforcement, military and energy market specialists before a recommendation is made to ministers and an operation is executed,” the release stated. “Following the detention of a ship, criminal proceedings may be brought against the owners, operators and crew, for breaches of UK sanctions legislation.”

Sir Keir Starmer said the UK would join northern European allies in interdicting ‘shadow fleet’ vessels as part of a drive to ‘go after’ the sanctioned ships fuelling Putin’s war in Ukraine.

He said: “Putin is rubbing his hands at the war in the Middle East because he thinks higher oil prices will let him line his pockets.”

Officials estimate that around 75% of Russia’s crude oil is transported through the ‘shadow fleet.’ The UK, alongside its allies, has imposed sanctions on 544 Russian ‘shadow fleet’ vessels and is calling for increased coordination to disrupt their operations further.