A union is warning that ships with a connection to Russia could reach the UK despite a Government ban because of “confusion” over sanctions.

Unison said two tankers, the Boris Vilkitsky and Fedor Litke, carrying gas, have been diverted from the Isle of Grain in Kent.

The union’s head of energy Matt Lay said: “These tankers appear to have gone away for now, but the cargo could be back on other ships within days.

“Transport Secretary Grant Shapps and other ministers must deal with this issue properly.

“Even ships with a clear Russian connection are causing confusion and could slip through the net to reach a UK port.

“Department for Transport rules only cover the ownership and operators of vessels, not the cargo.

“The Government also needs to clarify what it means by operators.

“The Boris Vilkitsky was chartered by a company based in Singapore, but majority Russian-owned.

“It’s not at all clear whether it’s covered by the ban.

“The Transport Secretary claims all ships with Russian connections are now barred from UK ports, but companies are free to get around the rules by hiring ships from other countries to import Russian goods.

“The Government should act right away if these sanctions are to be fit for purpose.”

A Government spokesperson said: “UK Government ministers have signed legislation banning all ships that are Russian owned, operated, controlled, registered or flagged from entering British ports.

“It is mandatory for all ports and harbours to follow this legislation and the Government will support all ports in exercising their responsibilities.

“We will continue to isolate (Vladimir) Putin through every means as he carries out these illegal and inhumane action.”

Unite joined calls for a loophole to be closed after revealing the case of a tanker sailing under a German flag understood to be carrying Russian oil and heading for the Stanlow terminal in the North West.

General secretary Sharon Graham said: “Unite has today contacted Essar who operate the Stanlow oil refinery to inform the company that due to the ongoing conflict in Ukraine, Unite workers at the facility will under no circumstances unload any Russian oil regardless of the nationality of the vessel.

“Unite urges Grant Shapps to close this loophole immediately.”

A Government spokesperson said: “It is mandatory for all ports and harbours to follow legislation banning all ships that are Russian owned, operated, controlled, registered or flagged from entering British ports. The Government will support all ports in exercising their responsibilities.

“We’ll continue to monitor the impact of the situation, but the UK has no issue with gas supply, and unlike other countries in Europe, the UK is in no way dependent on Russian gas, with imports making up just 4% of demand.

“Ministers are exploring options to further reduce the already small amount of imports we do get from Russia and we continue to urge Europe to put in place plans to end their dependence in Russian gas.”

Stanlow operator Essar said in a statement: “Essar remains deeply concerned by the humanitarian crisis unfolding in Ukraine and is fully complying with the statutory framework implemented by the UK Government with regard to Russia-related entities. Earlier this week, we turned away two cargos of non-Russian origin crude oil which would have been delivered in Russian-flagged tankers.

“We can confirm that a German-flagged vessel was approved to berth at Tranmere Oil Terminal by the Port Authority on Thursday March 3.

“This vessel set sail for Tranmere on February 22, before the invasion of Ukraine and the subsequent introduction of UK Government sanctions.

“For a number of days, we have been working urgently to find alternative sources of diesel while simultaneously ensuring uninterrupted supply of fuel to the North West of England.

“Essar will continue to comply fully and will respond promptly to any changes the UK Government may make to the statutory framework of sanctions.”