The “only effective means available” of ensuring Shamima Begum has a fair and effective appeal against the removal of her British citizenship is to allow her to return to the UK, the Supreme Court has heard.

Shamima Begum was 15 when she and two other east London schoolgirls travelled to Syria to join the so-called Islamic State group (IS) in February 2015.

Her British citizenship was revoked on national security grounds shortly after she was found, nine months pregnant, in a Syrian refugee camp in February last year.

Ms Begum, now 21 and currently in the al-Roj camp in northern Syria, where conditions are said by her lawyers to be “dire”, is challenging the Home Office’s decision to remove her British citizenship and wants to be allowed to return to the UK to pursue her appeal.

In July, the Court of Appeal ruled that “the only way in which she can have a fair and effective appeal is to be permitted to come into the United Kingdom to pursue her appeal”.

However, the Home Office argues that allowing her to return to the UK “would create significant national security risks” and expose the public to “an increased risk of terrorism”.

On the second day of a remote hearing on Tuesday, Ms Begum’s lawyers argued that she “cannot play a meaningful part in her appeal” and must be allowed to return to the UK to challenge the removal of her citizenship.

Her barrister Lord Pannick QC said that, if Ms Begum could not return to the UK to pursue an effective appeal, “the deprivation appeal must be allowed” as there is “no other fair or just step that can be taken”.

He told the court that the Government “cannot maintain a decision to deprive Ms Begum of her citizenship unless a means can be conferred on her, without unreasonable delay, (to have) a meaningful opportunity to appeal”.

Lord Pannick added: “Leave to enter (the UK) is the only effective such means available.”

Lord Pannick said in written submissions that the Syrian Democratic Forces, which control the al-Roj camp, “do not permit visits from lawyers nor do they permit detainees to speak to lawyers”.

He said Ms Begum was therefore “unable to give instructions on any detailed issues of fact” or review the national security case relied on by the Home Office in relation to “IS and the situation in Syria during the relevant period of time”.

He added that the case against Ms Begum was “no more than that she travelled to Syria and ‘aligned with IS'”.

He said: “It is not alleged that she fought, trained or participated in any terrorist activities, nor that she had any role within IS.

“It is not said that she has expressed or harbours any ill will against the United Kingdom.”

On Monday, Sir James Eadie QC, representing the Home Office, told the court: “If you force the Secretary of State to facilitate a return to the UK, or if you allow the substantive appeal, the effect is to create potentially very serious national security concerns.”

He said of Ms Begum: “She married an IS fighter, lived in Raqqa, the capital of the self-declared caliphate, and remained with them for about four years until 2019, when she left from, in effect, the last pocket of IS territory in Baghuz.”

Sir James argued that individuals who went to Syria to join IS pose a “real and serious” risk to national security “whatever sympathy might be generated by the age of the person when they travelled”.

In written submissions, Sir James said: “This case raises questions as to the balance to be struck between degrees of protection of procedural rights and degrees of protection of the public from terrorism.

“Can it be right that a person who has involved themself in terrorism, and is now abroad and subject to restrictions that affect their ability to participate in domestic proceedings, is able to rely on those self-created impediments to insist on return to the jurisdiction to enable them to participate now in such proceedings?

“Can it be right that they should be able to do so if enabling them to do so runs directly contrary to the most effective protection of the public from the risks of harm through terrorism?”

Kadiza Sultana and Amira Abase, then 16 and 15 respectively, and Ms Begum boarded a flight from Gatwick Airport to Istanbul, Turkey, on February 17 2015, before making their way to Raqqa in Syria.

The three schoolgirls from Bethnal Green Academy left London shortly after Sharmeena Begum, who is no relation, travelled to Syria in December 2014.

Ms Begum claims she married Dutch convert Yago Riedijk 10 days after arriving in IS territory, with all three of her school friends also reportedly marrying foreign IS fighters.

She told The Times last February that she left Raqqa in January 2017 with her husband, but her children, a one-year-old girl and a three-month-old boy, had both since died. Her third child died in the al-Roj camp in March 2019, shortly after he was born.

At the conclusion of the two-day hearing on Tuesday, the Supreme Court’s president Lord Reed said the court would deliver its judgment at a later date.