Dozens of Russian oil tankers under UK sanctions have passed through the English Channel this month despite government vows of "assertive action," reports BBC News.

BBC Verify tracked 42 sanctioned vessels transiting the Channel after officials received legal advice that such ships could be detained. Among them was the Sofos, sanctioned in May 2025, which travelled from Venezuela and is now near Saint Petersburg.

Ship-tracking data showed the Sofos loaded oil in Russia in November, then sailed to Turkey and Venezuela, switching off its signal before reappearing outside Venezuelan waters in late December. Another vessel, the Nasledie, more than 20 years old, entered the Channel in January carrying 100,000 tonnes of Urals crude.

Analysts said Russia's "shadow fleet" of ageing tankers with obscured ownership has helped Moscow evade sanctions since 2022. Foreign Secretary Yvette Cooper pledged to "tighten the chokehold" on Russia, saying troops could board and seize vessels under the Sanctions and Money Act 2018.

While UK forces assisted US and French allies in recent seizures, British troops have yet to independently intercept any tankers. BBC Verify identified six vessels operating under false flags in January, which under international law could be seized as stateless.

Dame Emily Thornberry, chairwoman of Parliament's Foreign Affairs Committee, said she was "very disappointed" the ships had not been intercepted. Liberal Democrat MP Mike Martin questioned why the UK has not acted, noting Royal Marines are trained for such operations.

Russia has responded with warnings. A warship escorted the sanctioned General Skobelev through the Channel, while Moscow said any detention would violate international law.

Other tankers sanctioned by the US and EU also transited the Channel. One vessel, the Arcusat, previously sanctioned as the Tia, obtained a new IMO number and was labelled "the darkest of the dark fleet" before being stopped by German police.

Analysts estimate Russia's shadow fleet moves between US$87 billion and $100 billion of oil annually. In December 2025, 68 per cent of Russian crude was carried on sanctioned tankers. Martin said the fleet provides Moscow with an economic lifeline, adding the war will only end "when Russia's economy collapses."