Shamima Begum, the woman who left Britain as a schoolgirl to join Islamic State in Syria, has launched an appeal against the Home Office’s move to revoke her citizenship and prevent her from returning to London.

At a partially secret hearing before the Special Immigration Appeals Commission (Siac), lawyers for Begum, who is now 20, alleged she had been left stateless, was unable to mount a “fair and effective” legal challenge and was at risk of “death, inhuman or degrading treatment”.

If she was forced to go to Bangladesh, her parents’ country of origin, she was at risk of being hanged, the court was told.

Begum, who was born in the UK, grew up in east London. The court was told there was no evidence she had ever visited Bangladesh or applied for citizenship there. In February 2015, when she was 15, she left her home with two other teenagers and travelled to Syria.

She disappeared from western sight until February 2019, when she was discovered by journalists in al-Hawl refugee camp, in Syria, following the collapse of the Isis caliphate. The camp is guarded by Kurdish militia.

During her time in Syria, Begum gave birth to three children, all of whom have died. In February last year, she was moved to another camp, al-Roj, following threats against her. She has denied comments she initially made while in al-Hawl, saying that she had to protect herself.

In a later interview with the Daily Mail, the court was told, Begum stated: “I hate the Dawla [Isis’s name for itself] so much. I hate these women and what they stand for and what they believe in and that they think they can terrorise anyone who does not share their views.”

Siac is not considering whether Begum poses a risk to national security. It heard a short outline of the case before going into secret session.

She was deprived of citizenship on 19 February 2019. Her youngest child died three weeks later.

In written submissions Tom Hickman QC, representing Begum, said she had spent her time in Syria waiting at home for her husband, who had been imprisoned and accused of spying. Her days were taken up with caring for her children. She did not speak Arabic.

Conditions in al-Roj were reported to be “squalid” and wretched. The court heard al-Roj was “likely to be unguarded” in the aftermath of this month’s Turkish invasion of the northern part of Kurdish-controlled Syria, and that the environment there “is likely to be incredibly fragile and dangerous”.

Hickman told the court: “[Begum] intended to return to the UK when the British government, after hearing of that intention, deprived her of her British citizenship with the purpose of preventing her from returning to the UK.

“Those actions were motivated, at least in part, by a desire to prevent the appellant exercising her [human rights] in the UK (such as by resisting deportation to Bangladesh).”

Begum has limited means of communicating with her solicitor, Daniel Furner, from the law firm Birnberg Peirce, Hickman said.

Lawyers for the Home Office did not immediately release their submissions to the court.

Bangladesh has officially denied Begum has dual citizenship, saying she is a British citizen by birth and has never applied for Bangladeshi nationality. The Home Office’s decision to deprive her of British citizenship therefore “rendered her stateless”, Hickman told the court. It was illegal, under international law, to make any citizen stateless and therefore the decision was unlawful, he said.

Expert evidence submitted to the court by Begum’s lawyers stated Bangladesh was ranked low down on the transparency international’s corruption index, its judiciary having been identified as one of the most corrupt sectors.

The current ruling party, the Awami League, is said to be strongly anti-Islamist and terrorist suspects are regularly subject to arbitrary detention or reportedly killed in shootings.

The deprivation of Begum’s citizenship, Hickman said, “has abandoned the appellant in a detention camp which she has no foreseeable prospect of leaving”. He continued: “Conditions at Roj are wretched and squalid. Humanitarian conditions are dire and the camps are significantly over-crowded. In a two-month period, 35 children died from cold or malnutrition in al-Hawl.”