Shamima Begum’s lawyers have said they will “keep fighting” after the 24-year-old lost a challenge over the removal of her British citizenship at the Court of Appeal.

Last year, Ms Begum lost her first appeal against the decision to revoke her citizenship on national security grounds at the Special Immigration Appeals Commission (SIAC), after she was found in a Syrian refugee camp following her travel to the country as a 15-year-old in 2015.

And on Friday, three judges at the Court of Appeal unanimously dismissed Ms Begum’s bid to overturn the SIAC decision.

Renu, eldest sister of Shamima Begum, holds a picture of her sister while being interviewed by the media in central London. Picture: Laura Lean/POOL/AFP via Getty Images

The Lady Chief Justice Baroness Carr said any arguments over the consequences of the unanimous judgment, which could include a bid to appeal at the Supreme Court, would be adjourned for seven days.

Speaking outside the Royal Courts of Justice after Friday’s short hearing, Ms Begum’s lawyers said they were processing the judgment, which they had only received on Friday morning.

Solicitor Daniel Furner said: “I think the only thing we can really say for certainty is that we are going to keep fighting. I want to say that I’m sorry to Shamima and to her family that after five years of fighting, she still hasn’t received justice in a British court and to promise her and promise the government that we are not going to stop fighting until she does get justice and until she is safely back home.”

In a summary of the decision, Baroness Carr, sitting with Lord Justice Bean and Lady Justice Whipple, said: “It could be argued the decision in Ms Begum’s case was harsh. It could also be argued that Ms Begum is the author of her own misfortune.

“But it is not for this court to agree or disagree with either point of view. The only task of the court was to assess whether the deprivation decision was unlawful. Since it was not, Ms Begum’s appeal is dismissed.”

At the appeal hearing in October, Samantha Knights KC told the court the government had failed to consider the legal duties owed to Ms Begum as a potential victim of trafficking or as a result of “state failures” in her case.

However, in the 42-page public judgment, Baroness Carr said: “We are not persuaded that there was any obligation on the Secretary of State to take into account the possibility that there might be a duty to investigate the circumstances of Ms Begum’s trafficking, alternatively, to consider whether any such investigation as might be required would be enhanced by her presence in this country.”

Baroness Carr added: “Ms Begum may well have been influenced and manipulated by others, but still have made a calculated decision to travel to Syria and align with Isil.”

Following the ruling, a Home Office spokesperson said: “We are pleased that the Court of Appeal has found in favour of our position in this case. Our priority remains maintaining the safety and security of the UK and we will robustly defend any decision made in doing so”.

The decision was also welcomed by Downing Street. “We’re pleased the court has found in favour of the Government,” a No.10 spokeswoman said.

Shamima Begum loses Court of Appeal challenge over removal of British citizenship