The Ukrainian president, Volodmyr Zelenskiy, will attend an extraordinary meeting of the British cabinet on Friday to bring fresh impetus to efforts to stop Russia evading sanctions on its oil exports.
Zelenskiy will be the first foreign leader to visit Downing Street since Keir Starmer was elected prime minister two weeks ago and the first foreign leader to address cabinet in person since the US president Bill Clinton in 1997.
The visit comes after EU leaders, who on Thursday gathered for the European Political Community summit in Blenheim Palace, Oxfordshire, agreed to launch a “call to action” to disrupt the growing fleet of “phantom” tankers carrying sanctioned Russian oil around the world.
Starmer said European leaders had sent a clear message to those acting as enablers for Putin. “We will not allow Russia’s shadow fleet, and the dirty money it generates, to flow freely through European waters and put our security at risk,” he said.
This will be Zelenskiy’s second visit to the UK since the war broke out. He last travelled to Britain in February 2023, when he gave a speech in Westminster Hall calling for the UK to supply Ukraine with fighter aircraft.
Since Russia invaded Ukraine in February 2022, the number of oil tankers masking their identity and running without proper insurance has increased, allowing the Kremlin to build a “dark fleet” and maintain oil revenues to fuel Russia’s war machine.
The maritime analyst Lloyd’s List Intelligence said the numbers of such vessels had doubled in the past year.
The shadow fleet is made up of about 600 vessels and represents about 10% of the global “wet cargo” fleet. It carries about 1.7m barrels of oil a day, generating significant revenue for Russia, the British government said.
Some of the ships are also alleged to double as Russian listening stations, while others are believed to be transporting weaponry to Russia.
Starmer is expected to tell Zelenskiy that the UK will go further to try to get a stranglehold on the phantom fleet – a matter also raised by the French president, Emmanual Macron, at the end of the summit in Blenheim.
It is understood the defence ministers of both countries will also sign a defence export support treaty to boost weapons supply to the battlefield. It is said to be designed “to fire up both the UK and Ukraine’s industrial bases and increase military hardware and weaponry production”.
It will include £3.5bn to support Ukraine’s armed forces, boosting a similar amount recently agreed by the EU to help with the maintenance of public services in the country, including schools and hospitals.
At the same time, Simon Harris, the Irish prime minister, and Starmer have also expressed interest in giving further support to Ukraine in the form of bomb shelters in schools.
Zelenskiy invoked the “bravery of Churchill” in his address to European leaders, telling them they had “maintained unity in Europe by acting together”. He also publicly took aim at the Hungarian prime minister, Viktor Orbán, accusing him of betraying fellow European leaders after his recent “peace mission” to Moscow.
Referring to Putin, he said: “He may try to approach you, or go to some of your partners individually, trying to tempt or pressure you to blackmail you, so that one of you betrays the rest. We keep our unity.”
In an apparent reference to Orbán’s recent visit to meet Putin, he added: “If someone in Europe tries to resolve issues behind our backs, or even at the expense of someone else, if someone wants to make some trips to the capital of war to talk – and perhaps promise something against our common interests or at the expense of Ukraine or other countries – then why should we consider such a person?”
The head of Nato, Jens Stoltenberg, who also attended the summit, implored European leaders to engage with Donald Trump and JD Vance if they won the US elections in November.
He said Europe must not fall into the trap of creating a “self-fulfilling prophecy” that Nato would die under a second Trump presidency and that the transatlantic bond would be over.
He said: “I think it’s important not to create self-fulfilling prophecies in a way that assuming that a new administration in the US will mean the end of Nato. There were concerns about that also in 2016. The reality was that Nato is stronger after four years … more troops, high readiness.”
