LONDON — The British government has told the family of Shamima Begum, a 19-year-old woman who traveled to Syria to marry an Islamic State fighter four years ago, that it intends to revoke her citizenship, according to a family lawyer.

Through a statement released by the lawyer, Tasnime Akunjee, Ms. Begum’s family said it was “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,” it added.

In a letter sent to Ms. Begum’s mother and obtained by the broadcaster ITV News, the British Home Office said the decision had been made by Home Secretary Sajid Javid on Tuesday.

Ms. Begum will be allowed to appeal the order through the courts, according to the letter.

British law prevents the government from stripping someone’s citizenship if doing so would render the person stateless. But British news outlets reported that because Ms. Begum’s mother has a Bangladeshi passport, the Home Office decided that it could remove her British citizenship.