British maritime authorities are intensifying their campaign to crack down on Russia’s illicit oil exports by challenging dozens of suspicious vessels each month in the English Channel. According to new government data, 343 vessels were questioned between October 2024 and June 2025, mostly tankers suspected of being part of Russia’s “shadow fleet.”

These vessels are used by Moscow to circumvent Western sanctions imposed after its full-scale invasion of Ukraine in 2022. Often sailing without western insurance and using opaque ownership structures, shadow fleet tankers deliver Russian crude and refined products to buyers in India, China, and other countries.

How the UK Is Acting

The UK government said it is now issuing radio challenges to ships as they approach British waters, demanding proof of insurance and regulatory compliance. While all ships are legally entitled to innocent passage, the UK maintains the right to question and sanction non-compliant vessels.

In one notable case, the tanker Ksena failed to respond to a UK request on November 12 and was later placed on the UK sanctions list. Officials say blacklisting vessels—rather than corporate owners—has proven more effective in cutting their access to business and maritime services.

“The UK is continuing to take steps to combat malign, Russian-backed maritime activity near the UK,” the government said in a statement. “We will continue to do so for any vessels we suspect.”

A Growing European Campaign

The UK’s initiative is part of a broader European push to curtail the safety and environmental risks posed by the shadow fleet. Western insurers are banned from covering tankers that carry Russian oil priced above a $60-per-barrel cap, meaning many shadow fleet vessels operate without adequate coverage.

In December, the UK, Denmark, Sweden, Poland, Finland, and Estonia agreed to intensify inspections. More recently, Germany and Sweden have increased checks on vessels transiting the Fehmarn Strait near the Baltic Sea.

A report from the Kyiv School of Economics estimated that in April 2025 alone, 692,000 barrels of crude and 245,000 barrels of refined products were exported from Russia’s Baltic ports on ships lacking recognized insurance.

Are the Measures Working?

Despite the scale of the effort, maritime analysts express doubt over the practical impact. One expert told the Financial Times that many ships either provide false information or ignore the UK’s questions entirely. “What follows appears to be fobbing off with false information or just ignoring those questions,” the expert said.

Still, officials argue that the challenges disrupt operations, raise compliance costs, and lay the groundwork for tougher future enforcement, particularly when combined with EU and G7 efforts.