The Home Office’s refusal to disclose the number of women who, like Shamima Begum, have been deprived of their British citizenship after travelling to join Islamic State is under investigation by the information commissioner. The watchdog said it would step in after the government refused to share the data with a human rights group concerned about the conditions of British women and children detained in camps in north-east Syria, where conditions are dire. Alison Huyghe, advocacy officer with Rights and Security International, accused the Home Office of engaging in a “dogged refusal” to disclose data, meaning that the policy of removing British citizenship was “beyond all oversight”. “We need to know about any risk of discrimination or other patterns of gender-related harm when the government takes people’s British citizenship away,” she added. Ministers have aggressively pursued a policy of taking away UK citizenship from Britons picked up following the fall of Isis at the end of the 2010s, arguing that they pose a national security threat and should not be allowed to return. British law allows the home secretary to take away somebody’s nationality if doing so is deemed “conducive to the public good” – although it is illegal to render somebody stateless if they are not eligible for citizenship of another country. A legal challenge from Begum failed in the supreme court last month, although her lawyers continue to consider their options. But two other women, known only as C3 and C4, who had also travelled to Syria, overturned a deprivation decision after a court ruled that they could not have claimed Bangladeshi citizenship. Estimates suggested that there remain about 15 women with 35 children being held by the Syrian Kurds, with no assistance from the UK. But their exact number and how many have been deprived of their citizenship have not been made public. They are among several thousand women and children from dozens of countries held in at least three impoverished camps in north-east Syria, but who have nowhere to go as their countries of origin have largely refused to take them back. Violence and malnutrition is rife and there are concerns about the radicalisation of those who remain in the camps, particularly in the largest, al-Hawl, which was the subject of a two week security operation, starting on Sunday. Rights and Security International said in a report produced last year that the effect of the policy was to subject women and children to “indefinite unlawful detention” in a situation with echoes of Guantánamo Bay. It argued that they should be brought back to their homelands “to face justice” if necessary. Ministers took away the British nationality of 23 people between 2014 and 2016 as the Isis terror group took large swaths of territory in Syria and Iraq, plus a further 104 in 2017 and 21 in 2018. No gender breakdown was provided. No data has been released since, prompting Rights and Security International to ask in a freedom of information request how many people had had their UK citizenship removed in 2019 and 2020, how many were women, and how many were parents of children under the age of 18 at the time the decision was made. The Home Office had said it would release headline figures covering 2019 and 2020 in due course, but any data relating to the number of women affected would not be released, citing an exemption clause in the Freedom of Information Act that says publishing the data would prejudice the conduct of public affairs. Leigh Day, lawyers for Rights and Security International, then appealed to the Information Commissioner’s Office, which replied that it had accepted the case “as eligible for further consideration”. A Home Office spokesperson said that deprivation of figures are published annually as part of a transparency report on Disruptive and Investigatory Powers that is due to be released shortly. “Where requests are made for details already due for publication or already publicly available, the Freedom of Information Act does not compel disclosure,” the spokesperson added.