Shamima Begum is not a Bangladeshi citizen and there is “no question” of her being allowed into Bangladesh, the country’s ministry of foreign affairs has insisted, setting up a clash with the UK after Sajid Javid’s move to strip the teenager of her UK citizenship.

“The government of Bangladesh is deeply concerned that [Begum] has been erroneously identified as a holder of dual citizenship,” Shahriar Alam, the state minister of foreign affairs, said in a statement issued to the Guardian, adding that his government had learned of Britain’s intention to cancel her citizenship rights from media reports.

“Bangladesh asserts that Ms Shamima Begum is not a Bangladeshi citizen. She is a British citizen by birth and never applied for dual nationality with Bangladesh … There is no question of her being allowed to enter into Bangladesh.”

The strongly worded statement is a direct challenge to Javid, the home secretary, who told MPs earlier on Wednesday that he would not waver in his determination to deprive the 19-year-old, who fled to Syria four years ago to marry an Islamic State fighter, of her citizenship.

With the two countries apparently settling on different interpretations of Bangladeshi immigration law and whether the country is obliged to extend citizenship rights to a 19-year-old of Bangladeshi heritage, Begum herself insisted that she would be left stateless if she lost her British citizenship.

Play Video 2:44 UK citizenship decision is heartbreaking, says Shamima Begum – video

She told the BBC: “I have one citizenship … and if you take that away from me, I don’t have anything. I don’t think they are allowed to do that.”

“This is a life-changing decision and they haven’t even spoken to me.”

The Foreign Office was understood to be in touch with the Bangladeshi high commission, but the FCO has stressed that decisions on Begum’s return were a matter for the Home Office. There is said to be some disquiet in ministerial circles that Bangladesh had not been consulted fully before the home secretary asserted she could claim Bangladeshi citizenship.

The FCO’s own website points out that Bangladesh is facing a fight to defeat terrorism, including from groups linked to Isis. Sources suggest that given this domestic fight against terrorism, it was never likely that Bangladesh would allow her in, regardless of the citizenship rights she was able to claim.

Javid insisted on Wednesday night that he “would never make any decision that would make an individual stateless” but failed to respond to Bangladesh’s stance on ITV’s Peston show, saying he could not discuss individual cases. He said: “My number one job is to do whatever I can to keep this country safe.”

The home secretary said he had to weigh up the law and the impact on people’s lives as well as any potential risk of returners trying to radicalise people in the UK. “In certain circumstances we will remove them of their nationality. I won’t hesitate to do that if that is the only option to me to keep people safe in the United Kingdom,” he said on the programme. “There’s a number of things that need to be in place … one of those is to make sure if you do go ahead and strip them of their nationality you do not leave them stateless.”

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In a measure of the complexities of the case, however, he indicated that the citizenship rights of Begum’s baby son, who was born just days before the government moved to deprive her rights, are unaffected.

Responding earlier to an urgent question on the case in the House of Commons, Javid said: “Children should not suffer, so if a parent loses their British citizenship it does not affect the rights of their child.”

In a letter dated 19 February, the government informed Begum’s family that it had stripped her of her British citizenship. The 19-year-old was one of three schoolgirls who left their home in Bethnal Green, east London.

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Begum, who is living with her son in a refugee camp in northern Syria, is of Bangladeshi heritage but she has said that she does not have a Bangladeshi passport and has never been to the country.

It is illegal under international law to deprive someone of their nationality if to do so would leave that person stateless.

Bangladeshi law includes a right of “citizenship by descent” to anyone who is born to a Bangladeshi parent.

Facebook Twitter Pinterest Shamima Begum left the UK for Syria when she was 15. Photograph: PA

Javid said the power to remove citizenship had been used 150 times since 2010, in the cases of people linked to terrorism and serious crimes.

He was challenged in parliament by the shadow home secretary, Diane Abbott, who said that the decision to deprive Begum “appears to have been taken on a wholly arbitrary basis”.

She pointed out that the government had been defeated in two previous cases where it had similarly sought to strip citizenship from people on the basis that, having Bangladeshi parents, they were themselves citizens.

In the most recent case, the special immigration appeals commission found that two terror suspects – codenamed E3 and N3 – were not dual nationals and so would have been rendered stateless. The government’s appeal against the decision will be heard later this year.

The lawyer who acted in that case, Fahad Ansari, said that while the court accepted the men had been Bangladeshi citizens by descent, “once they reach the age of 21 that citizenship lapses unless they actively seek to retain. Both my clients were over 21. But as far as Shamima Begum stands, she is 19, which is problematic for her.

“It’s quite bizarre because it leaves people like her, who are younger and more vulnerable to make silly mistakes like this, to be deprived, whereas people who are mature adults and make their decision to join IS, they are protected.”

The Begum family’s lawyer has said they are “considering all legal avenues” to challenge the decision.