British ISIS fighters can be legally stripped of their citizenship, the London high court has said in a ruling that gives legal backing for the controversial government policy.

Abdullah Islam challenged a call by former Home Secretary Amber Rudd in 2017 to deprive his 22-year-old son Ashraf Mahmud Islam, of his British nationality.

At the time, Ms Rudd said that she didn’t think that Ashraf would be made ‘stateless’, as he also had Bangladeshi citizenship. She warned that Ashraf was assessed as posing a risk to “national security”.

Ashraf travelled to Syria in April 2015 when he was 18 and studying A-level law at a British school in Dhaka, Bangladesh.

He is now being held in a Kurdish-run military prison in Syria. The ISIS fighter would only travel back to Britain if he is first released by the Kurds and then freely allowed by the Syrian authorities to leave the country but now cannot use British identity documents to do so.

Abdullah said he wanted his son to be brought back to the UK to face justice and be protected from facing the death penalty.

However, his case was rejected by the judge on Wednesday for having ‘no merit’.

Mr Justice Pepperall said: “The only action taken by the home secretary in this case has been to deprive Ashraf of his citizenship.

“He is not in peril in Syria because of that decision, but because he is being held on suspicion of involvement in the ISIS insurgency.”

The judge said that because Ashraf was born in London and was living with family, he appeared to have “every advantage in life”.

Justice Pepperall noted that after Ashraf joined the terrorist group, he gave an interview with ITV news saying that he had made a mistake and he wanted to return to the UK to face justice. However, the judge said Ashraf made these comments “with masterful understatement”.

Earlier this year, former home secretary Sajid Javid revealed that more than 100 dual nationals who travelled to join ISIS have had their UK citizenship stripped by the British Home Office.

Two members of the infamous “Beatles” group, which was led by Mohammed Emwazi and routinely beheaded Western hostages on camera, have been deprived of their citizenship.

Alexanda Kotey and El Shafee Elsheikh were captured in northern Syria in January 2018 and are now being held by Western-backed Kurdish forces in the war torn country.