In a statement posted on Twitter, he said: “Family are very disappointed with the Home Office’s intention to have an order made depriving Shamima of her citizenship.
“We are considering all legal avenues to challenge this decision.”
A letter written to the family on behalf of Home Secretary Sajid Javid and seen by ITV News confirmed the decision had been made to revoke the citizenship of Shamima Begum, 19, who it is believed gave birth last week.
The teenager, from Bethnal Green in East London, travelled to Syria to join with the self-styled Islamic State in 2015 and was discovered by a newspaper journalist in a refugee camp last year.
Mr Javid’s decision will almost certainly face legal scrutiny, as the UK is presently unable to render citizens born in the country stateless, and the revocation of citizenship is usually used against those with dual citizenship, or who became naturalised British citizens.