Labour's shadow home secretary Diane Abbott said: "If the government is proposing to make Shamima Begum stateless it is not just a breach of worldwide human rights law but is a failure to meet our security obligations to the global community".
Amarnath Amarasingam is a Senior Research Fellow at the Institute for Strategic Dialogue and a Postdoctoral Fellow at the University of Waterloo where he has been co-directing a study of Western foreign fighters for six years.
The letter comes after Ms Begum was found living in a Syrian refugee camp by a journalist from The Times. Both children have died, apparently from illness and malnutrition. White converts to Islam who joined ISIS, for instance, would get to keep their citizenship and be treated like any other criminal.
"I'll do anything required just to be able to come home and live quietly with my child", she said.
"I'm afraid he might even die in this camp".
Speaking during News Hour, he said her citizenship should "not be returned to her because when she went to the country she knew that there are punishments and laws and she broke the law".
But her plea for mercy from the British government fell on deaf ears and at the weekend she gave birth to a baby boy named Jerah inside the dismal crowded camp - named after a 7th-century Islamic warlord.
In a series of interviews with British media, she criticized some aspects of the Islamic State group and its self-proclaimed caliphate but said she does not regret going there. "Pres Assad's wife still has her British citizenship".
"But where this occurs, those children need legal-aid and support to ensure no child is denied their right to citizenship", UNICEF said in an email to the Thomson Reuters Foundation.
"I don't have a card because they lost my card, so I have to run around to take care of my son now, when I am sick".
'In light of the circumstances of your daughter, the notice of the decision has been served on file today and the order removing her citizenship has subsequently been made.
Ms Begum is reportedly of Bangladeshi heritage so could have dual citizenship.
Worldwide law prohibits governments from rendering people stateless by revoking their only citizenship.
He has previously said that more than 100 individuals had already been deprived of their British citizenship.
Former Conservative home secretary Ken Clarke said that Ms Begum was "obviously British" and Mr Javid's stance could be "a great boost for jihadism".
"I did have a good time there".
On Monday, in an interview with the BBC, Ms Begum compared the Manchester Arena bombing to military strikes on Isis strongholds, calling the terror attack "retaliation". "In order to protect this country, he has the power to deprive someone of their British citizenship where it would not render them stateless".
"We do not comment on individual cases, but any decisions to deprive individuals of their citizenship are based on all available evidence and not taken lightly". It added it was "deeply concerned that she has been erroneously identified as a holder of dual citizenship shared with Bangladesh alongside her birthplace, the United Kingdom".
"She is a British citizen by birth and has never applied for dual nationality with Bangladesh", it said. It may also be mentioned that she never visited Bangladesh in the past despite her parental lineage.