Jeremy Corbyn has joined lawyers and human rights groups in defending the right of Shamima Begum to be granted legal aid so that the east London teenager can challenge the decision to remove her UK citizenship.

The Labour leader said that, whatever crimes Begum was accused of after she left the UK to join Islamic State in Syria, she was entitled to proper legal representation.

“She is a British national and therefore she has that right, like any of us do, to apply for legal aid if she has a problem. She has legal rights, just like anybody else does,” he told reporters on Monday.

“The whole point of legal aid is that if you’re facing a prosecution then you’re entitled to be represented and that’s a fundamental rule of law, a fundamental point in any democratic society.”

The foreign secretary, Jeremy Hunt, said the idea Begum could receive taxpayer funding to challenge the decision to remove her citizenship made him “very uncomfortable”.

“She knew the choices she was making, so I think we made decisions about her future based on those choices,” he said.

The row over Begum’s entitlement to publicly funded legal support grew further on Monday as the solicitor representing her family accused the government of breaching the Official Secrets Act by selectively leaking intelligence reports to sympathetic media, damaging her reputation.

Tasnime Akunjee, who represents the family, also revealed he was acting on behalf of others held in Syrian camps who had been stripped of their nationality rights. He said the number of such cases was likely to grow.

Akunjee is representing Begum’s family pro bono; they have not applied for legal aid. Begum’s case, however, has been transferred to the firm of Birnberg Peirce, which holds a legal aid certificate and has applied on her behalf for the financial support. The firm did not immediately confirm whether it had yet been awarded.

A Legal Aid Agency spokesperson said: “We are unable to comment on individual cases.

“Anybody applying for legal aid in a Special Immigration Appeals Commission [SIAC] case is subject to strict eligibility tests.”

Begum, now 19, should be allowed to appeal against the decision of the home secretary, Sajid Javid, to deprive her of her citizenship, Akunjee told the Guardian.

“[Javid] initiated a legal process and under that she’s entitled to appeal,” Akunjee said. “Legal aid enables her to fund that application with the help of solicitors. Those accused of serious crimes, such as rape, murder or terrorism, are regularly granted legal aid in the context of legal proceedings.”

He said he expected there to be a legal challenge, arguing that Begum should be able to return to the UK to fight the case in order to have a fair hearing.

Several newspapers at the weekend carried reports, which Akunjee said were based on intelligence sent to the Home Office and Downing Street, alleging that Begum was an enforcer working with the Isis morality police and had supposedly sewed up suicide bombers’ vests.

“I would question how that has come into the public arena and whether the Official Secrets Act has been breached,” Akunjee said. He described the reports as “mere hearsay” and said that “the leak appears to have come from government sources”.

Many senior figures accept Begum is entitled to legal aid. Hunt acknowledged that the UK was a country that believed “people with limited means should have access to the resources of the state if they want to challenge the decisions the state has made about them”.

The Law Society, which represents solicitors across England and Wales, also backed Begum’s entitlement to legal aid. In a detailed blog, the anonymous Secret Barrister urged the government to ensure “equal treatment before the law” by granting legal aid.

“The removal of a person’s citizenship – a government telling a British-born citizen ‘You have no right to exist within our borders’ – is one of the most far-reaching decisions the state can make. We do not want to live in a country where politicians can act with unchecked power,” the Secret Barrister argued. “The rule of law requires that those affected have a route to challenge a decision and have an independent court review the evidence and decide whether that decision was taken in accordance with the law.”

Dal Babu, a former chief superintendent in the Metropolitan police and a friend of the family, told BBC Radio 4’s Today programme that Begum was “groomed” by Isis and should be given legal aid, which is a “principle of the British legal justice system”.

Corey Stoughton, the advocacy director at the human rights group Liberty, described the granting of legal aid in this case as “absolutely necessary to ensure that the government’s decisions are properly scrutinised”.

She said: “Stripping someone of their citizenship is among the most severe punishments a government can exercise, and the evidence that this decision will render Shamima Begum effectively stateless presents a powerful argument for subjecting this case to rigorous scrutiny in court.

“This case could have widespread repercussions for thousands of people, and more broadly for how the government uses dramatic powers to take away fundamental rights.”