The prime minister is set to impose a new wave of sanctions on Russian oil tankers, which are being used to avoid existing sanctions imposed after the invasion of Ukraine.
Number 10 has said action will be taken against up to 100 vessels which have carried more than £18 billion worth of cargo since the start of 2024.
Sir Keir Starmer is due to make the announcement at a summit of north European leaders known as the Joint Expeditionary Force (JEF) in Oslo, Norway.
The PM has vowed the UK will do everything in its power to "destroy" President Putin's "shadow fleet operation, starve his war machine of oil revenues and protect the subsea infrastructure".
To get round these penalties, Moscow built up what has been referred to as a "shadow fleet" of tankers whose ownership and movements could be obscured.
Downing Street has accused the operation of "bankrolling the Kremlin's illegal war in Ukraine".
The government has referred to the ships as being "decrepit and dangerous" as well as being responsible for "reckless seafaring". It follows reports of damage to a major undersea cable in the Baltic Sea.
Under the measures, the sanctioned tankers will be banned from British ports and risk being detained in UK waters.
Starmer said every step that increases pressure on Moscow and works towards peace for Ukraine "is another step towards security and prosperity in the UK".
The JEF consists of ten nations including Denmark, Norway and the Netherlands.
Members of the JEF are also expected to announce further support for Ukraine's war efforts.
The UK previously imposed sanctions against 133 "shadow" vessels during a meeting of the JEF in December 2024.
