(BBC) — Shamima Begum, who joined the Islamic State group in Syria aged 15, is to lose her UK citizenship.
The family’s lawyer, Tasnime Akunjee, said they were “disappointed” with the decision and were considering “all legal avenues” to challenge it.
Ms Begum left Bethnal Green, east London, with two school friends in February 2015.
Now 19, she was found in a Syrian refugee camp last week after reportedly leaving Baghuz, IS’s last stronghold.
In a BBC interview, Ms Begum, who has just given birth to a son, had said she now wants the UK’s forgiveness and to return home.
ITV News said Ms Begum’s mother had received a letter from the Home Office on Tuesday.
The letter said Home Secretary Sajid Javid had taken the decision to remove her daughter’s British citizenship and the order to do so had subsequently been made.
It asked her mother to let Ms Begum know of the decision and inform her she has a right to appeal.
Whitehall sources confirmed the home secretary had taken the decision.
Under the 1981 British Nationality Act, a person can be deprived of their citizenship if the home secretary is satisfied it would be “conducive to the public good” and they would not become stateless as a result.
Ms Begum said she travelled to Syria with her sister’s UK passport but it was taken from her when she crossed the border.
She is believed to be of Bangladeshi heritage but when asked by the BBC, she said did not have a Bangladesh passport and had never been to the country.
A Home Office spokesman said while he could not discuss individual cases, “we don’t leave people stateless”.
Mr Javid told MPs on Monday he would not “hesitate to prevent” the return of Britons who travelled to Syria to join IS.
He said more than 100 dual nationals have already lost their UK citizenship after travelling in support of terrorist groups.
Willing to rehabilitate
Ms Begum has said she does not regret travelling to Syria and was partly inspired by videos of fighters beheading hostages, as well as by videos showing “the good life” under IS.
However, she said she did not agree with everything the group had done.
“I actually do support some British values and I am willing to go back to the UK and settle back again and rehabilitate and that stuff,” she told the BBC.
Ms Begum left the UK with two other schoolgirls, Kadiza Sultana and Amira Abase. Kadiza is thought to have died when a house was blown up, and the fate of Amira is unknown.
Ms Begum gave birth to a baby boy last weekend, having previously lost two children.
Her husband, a Dutch convert to Islam, is thought to have surrendered to a group of Syrian fighters about two weeks ago.