Islamic State bride Shamima Begum, who fled to Syria aged 15, is not a Bangladeshi citizen and will be barred from entering the country, its foreign ministry has said.
The 19-year-old from London said she wanted to return to the UK with her newborn baby, with the end of the so-called caliphate in Syria within sight.
But Home Secretary Sajid Javid revoked her British citizenship in a move only permissible under international law if it does not leave the individual stateless.
There had been speculation that Ms Begum, who is of Bangladeshi heritage, may have citizenship there but its minister of state for foreign affairs Shahriar Alam denied this on Wednesday.
A statement tweeted by the minister said: “The Government of Bangladesh is deeply concerned that she has been erroneously identified as a holder of dual citizenship shared with Bangladesh alongside her birthplace, the United Kingdom.
“Bangladesh asserts that Ms Shamima Begum is not a Bangladeshi citizen. She is a British citizen by birth and has never applied for dual nationality with Bangladesh.
“It may also be mentioned that she never visited Bangladesh in the past despite her parental lineage.
“So, there is no question of her being allowed to enter into Bangladesh.”
The statement added that Dhaka had only been made aware of the situation by the media.
Asked whether she had been left stateless by Britain, the Begum family’s lawyer Tasnime Akunjee said: “It’s certainly something we will be adding to the mix in terms of our appeal.”
He has said Ms Begum was born in the UK, has never had a Bangladeshi passport and is not a dual citizen.
Asked about the situation on ITV’s Peston, Mr Javid said: “I’m not aware of any Home Secretary in any party in any previous government that has taken a decision that would leave anyone stateless.
“I’m not going to talk about an individual, but I can be clear on the point that I would not take a decision and I believe none of my predecessors ever have taken a decision that at the point the decision is taken would leave that individual stateless.”
A Home Office spokesman said: “In recent days the Home Secretary has clearly stated that his priority is the safety and security of Britain and the people who live here.
“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.”
She was one of three schoolgirls to leave Bethnal Green to join the terror cult in 2015 and resurfaced heavily pregnant at a Syrian refugee camp last week.
On Wednesday, she was shown a copy of the Home Office letter that announced her British citizenship would be stripped.
She told ITV News: “I don’t know what to say. I am not that shocked but I am a bit shocked.
“It’s a bit upsetting and frustrating. I feel like it’s a bit unjust on me and my son.”
She went on to say she may try for citizenship in the Netherlands, where her husband is from.
Meanwhile, Mr Javid suggested the action to prevent Ms Begum returning will have no impact on her baby son’s nationality.
While insisting he could not discuss individual cases, he told the Commons: “Children should not suffer.
“So, if a parent does lose their British citizenship, it does not affect the rights of their child.”
He also delivered a staunch defence of the Government’s ability to use the citizenship powers to prevent the return of “dangerous individuals”.
He told MPs that the step was never taken lightly, adding: “But when someone turns their back on the fundamental values and supports terror, they don’t have an automatic right to return to the UK.
“We must put the safety and security of our country first and I will not hesitate to act to protect it.”
Ms Begum’s comments sparked intense debate about the UK’s responsibilities to those seeking to return from Syria.
The case took a dramatic turn on Tuesday when it emerged Mr Javid had opted to strip Ms Begum of her British citizenship.
The British Nationality Act 1981 provides the Home Secretary with the power to take such action if it is “conducive to the public good”.
A protracted legal battle over the move is now looming with international law forbidding nations from making people stateless.
Lord Carlile, former independent reviewer of terrorism legislation, said Ms Begum could challenge the decision, and described it as a “complex issue” that could take a while to resolve.
He told BBC Breakfast: “I suspect that the result is going to be that she will stay where she is for maybe two years at least.”
Figures for 2017 show that 104 people were deprived of their British citizenship, up from 14 in the previous year.