Campaigners have called on the British authorities to refuse permission for a vast Saudi ship carrying military equipment to dock in the UK because the Gulf kingdom is still embroiled in the war in Yemen.

The Bahri Yanbu is heading toward Sheerness docks, a few days after plans to dock at Antwerp were abandoned after protesters, calling themselves “citizen weapons inspectors”, set up a checkpoint to halt any flow of arms.

The container vessel had originally been expected to dock at Sheerness, Kent, on Wednesday morning, but remained, in the afternoon, a few miles off the coast, while campaign groups mounted a last-ditch attempt to prevent it from landing.

The law firm Leigh Day, which is representing Campaign Against the Arms Trade (CAAT), wrote to UK government lawyers to clarify whether the ship’s business was in line with an export ban on British arms to Saudi Arabia, which could be used in the Yemen war.

Andrew Smith of CAAT said: “This ship must be turned away. If it is carrying weapons for use in Yemen then they could be used in war crimes and abuses for years to come.”

He added: “Arms-dealing governments like the one in the UK have played a central role in strengthening the Saudi dictatorship and fuelling the devastating war in Yemen.”

Last July, the court of appeal ruled that all future arms exports to Riyadh that could be used in Yemen had to be halted because UK ministers and officials had failed to properly assess the humanitarian risks involved.

Britain is a major supplier to Saudi Arabia, having licensed at least £5.3bn worth of arms since 2015. Missiles made in the UK are used by British-supplied Typhoon jets in the Saudi airforce.

According to the Yemen Data Project, more than 8,630 civilians have been killed during the conflict, which began in 2015. Many have died as a result of more than 20,000 air raids by the Saudi-led coalition fighting Houthi rebels in the country.

Bahri, the state-owned shipping company that owns the Yanbu, confirmed to Belgian media that military equipment was onboard but denied it was to take on any such kit at Antwerp.

The ship has travelled from North America, where it has docked in the US and Canada, and is travelling around Europe before heading to Saudi Arabia and other nearby countries. It is meant to stop in Cherbourg and Genoa, where a dockworkers’ strike is planned.

On a previous visit to several European ports in May 2019, the vessel was carrying US-manufactured military components and equipment worth $47m (£36m), much of it linked to military aircraft, according to Amnesty International.

Containers of arms were loaded onboard in Belgium and Spain, and howitzer cannon were due to be loaded in France although pressure groups in the country successfully took legal action to halt the arms transfer at the time.