Tankers that breach the oil price cap must be banned from European Union and G7 ports as part of efforts to restore “integrity and credibility” to the tarnished scheme, according to researchers.

Leaders of the G7 group of nations insisted at the weekend that the oil caps are working, but a failure to enforce breaches has damaged efforts to target the Kremlin’s revenues, said Finland’s Centre for Research on Energy & Clean Air (CREA).