The home secretary is facing criticism after the baby son of Islamic State (IS) bride Shamima Begum died in Syria just weeks after the teenager was stripped of her British citizenship.
Syrian Democratic Forces confirmed on Friday night the boy, named Jarrah, had died - two days after being taken to hospital with breathing difficulties.
He was born in mid-February at the refugee camp where his 19-year-old mother has been staying, and had already been unwell in the weeks leading up to his death.
He was born before his mother lost her citizenship and was therefore a British citizen.
Shamima Begum - who has previously lost two children - told Sky News last month that she would not allow him to go to the UK alone as she pleaded to be allowed to return.
The decision by Home Secretary Sajid Javid to strip her of her British citizenship sparked a national debate over whether she should be brought back to Britain.
Following news of the boy's death, shadow home secretary Diane Abbott said: "The tragic death of Shamima Begum's baby, Jarrah, is a stain on the conscience of this government.
"It is against international law to make someone stateless. And to leave a vulnerable young woman and an innocent child in a refugee camp, where we know infant mortality to be high, is morally reprehensible."
She accused the home secretary of pandering to the right-wing press, saying: "Whenever there are reasonable grounds to suspect that someone who is entitled to return to this country has either committed or facilitated acts of terrorism, they should be fully investigated and where appropriate prosecuted.
"In an effort to appease the right-wing press, the Home Secretary would not even grant Shamima this."
She added: "The home secretary failed this British child and he has a lot to answer for."
Kirsty McNeill, executive director of policy, advocacy and campaigns at Save the Children UK, told Sky News: "This is an avoidable tragedy. It's worth baring in mind this little baby was not yet three weeks old and it's a British newborn... [he] died and has been buried in a teeming, freezing refugee camp far from here."
Ms McNeill said there are around 2,500 other children in the camps with foreign parents.
Conservative MP Andrea Leadsom, who is leader of the House of Commons, defended her colleague, saying: "It is absolutely tragic that a baby has died and of course I understand this is a really terrible problem.
But on the other hand, the job of the home secretary is to protect all the people in the United Kingdom.
"He will have had advice on what was the right thing to do and I totally support his decision."
Shamima Begum, from Bethnal Green in east London, was 15 when she and two other schoolgirls ran away from their homes to join IS in February 2015.
She resurfaced heavily pregnant in a refugee camp in northern Syria last month and spoke of her desire to return to the UK as the self-styled caliphate collapsed.
Following news of the death of Jarrah, a UK government spokesman said: "The death of any child is tragic and deeply distressing for the family.
"The Foreign and Commonwealth Office has consistently advised against travel to Syria since April 2011.
"The government will continue to do whatever we can to prevent people from being drawn into terrorism and travelling to dangerous conflict zones."
Mr Javid had insisted that Shamima Begum would not be left "stateless" because of his decision, amid speculation that she is a dual British-Bangladeshi national.
After the Bangladeshi government claimed she was not a Bangladeshi citizen, she told Sky News that she had no desire to go to the country.
She said: "I don't have anything there, another language, I have never even seen the place, I don't know why people are offering that to me."
The 19-year-old had previously told Sky News she was "okay" with beheadings by IS and claimed in another interview that the terror attack at the Manchester Arena was "retaliation" for bombings in Syria.
Asked if she had anything to say to British politicians, she said: "I would like them to re-evaluate my case with a bit more mercy in their heart, you know."
Her husband, Dutch IS fighter Yago Riedijk, admitted they had both made a mistake when they joined the terror group, but insisted his wife was not dangerous.
The 27-year-old, who is being held in a Kurdish detention centre in northeastern Syria, married Shamima just weeks after she arrived in IS territory in 2015.
When asked if the pair had made a mistake by joining the terrorist group, he replied: "Definitely."
He added: "I know (Shamima) is not a danger to anyone whatsoever... but she made a mistake and will have to live with the consequences.
"She never really did anything besides being a wife."
Last month, her sister, Renu, sent a letter to Mr Javid calling for Jarrah to be brought to the UK, saying he was "the one true innocent and should not lose privilege of being raised in the safety of this country".
In response, the Home Office said it was a matter for the Foreign Office and she would have to confirm she was authorised to make a request for consular assistance on her behalf.