The newborn baby of Shamima Begum is a British citizen and could return to the UK despite the teenage mother losing her citizenship over her support for the terror group Isil, according to lawyers.

Begum, 19, was told yesterday Home Secretary Sajid Javid had decided to strip her of her British citizenship, four years after she fled the UK to join ISIL in Syria and marry a Dutch-born Isil fighter.

As a result, she will be banned from Britain as her return would "not be conducive to the public good", a move that could only be taken because the Home Office claims she has dual British-Bangladesh nationality due to her parents being from Bangladesh.

Without dual nationality, it is illegal under international law to strip anyone of their British citizenship and leave them stateless.

While her lawyers are now considering appealing the move, The Telegraph can reveal that her baby, provided she can prove it is hers, is a British citizen because it was born at the weekend before she was stripped of her British citizenship on Tuesday.

“The baby was born prior to the deprivation order. The baby would have inherited British citizenship from the mother. The baby is British,” said Fahan Ansari, an immigration lawyer who won an appeal against the Government on behalf of two British-Bangladeshis stripped of their citizenship.