The UK and US have presented a united front in the battle against the shadow fleet with a public commitment to share information and run co-ordinated investigations.

A memo, published by sanctions enforcers for both countries, says they will advance their “common mission of investigating, enforcing and promoting compliance with economic sanctions”.

The move follows complaints by insurers that blacklists compiled by the US, UK and European Union were not aligned, adding legal complexity to the most wide-ranging sanctions regime imposed against a state.