British police are investigating Shamima Begum despite the government’s decision to remove her UK citizenship rather than repatriate her for trial.
The Metropolitan Police has applied for a judge to force three media companies to hand over their material after they refused voluntary requests.
A production order, under the Terrorism Act, requires officers to prove the material is “sought for the purposes of a terrorist investigation”, is of “substantial value” and that seizure is in the public interest.
A lawyer representing Ms Begum's family told The Independent he had not been informed of the application and believes police are “building a case against her”.
Tasnime Akunjee said a hearing date has not yet been set for an appeal against Sajid Javid’s decision to remove her British citizenship, which allegedly made her stateless.
“When you put the two together – the fact they’re stretching out the hearing and you’ve got police beavering away – it suggests that if she is brought back to the UK she will face legal proceedings,” he added.
A spokesperson for the Metropolitan Police would not tell The Independent why the application was made or confirm whether officers were gathering evidence for a potential prosecution.
“Officers will contact media organisations if they believe that they may have information or evidence that could assist a criminal investigation,” a statement said.
“We fully respect the media’s independence. The police will, when appropriate, seek a production order in situations where that material is not provided voluntarily.
“The decision to grant or deny the production order, quite properly, lies with the court.”
The Times, Sky News and ITN instructed legal representation to resist the application ahead of a hearing at the Old Bailey in London on Tuesday.
The case was due to be heard by Mr Justice Sweeney, a high court judge, but was adjourned after he ruled the case must be first heard by a circuit judge instead.
It will now be considered on Wednesday before Judge Mark Dennis QC, at the same court.
Only one in 10 of more than 400 jihadis who have already travelled back from Syria have been prosecuted and the government has introduced a suite of new terror laws aiming to make the move easier.
The UK has so far refused to repatriate captured British Isis fighters to face trial, despite mounting international pressure and pleas from Kurdish officials in Syria.
As home secretary, Mr Javid said he used citizenship deprivation powers to “protect the country” and prevent them from returning to the UK.
A Home Office source told The Independent that the government’s position on detained British jihadis has not changed since he was replaced by Priti Patel in Boris Johnson’s new cabinet.
Official guidance states that the home secretary can deprive citizenship for the “public good” if a person can apply for alternative nationality, but Bangladeshi officials said Begum was not a dual national and would not be allowed to enter the country.
Her lawyers are taking the case to the Special Immigration and Appeals Commission, which previously found the decision to remove British citizenship from two alleged Islamists of Bangladeshi heritage unlawful.
Ms Begum is currently detained in the Roj camp in Syria, alongside other women who joined Isis and their children.
She travelled to the terrorist group’s strongholds aged 15 with two school friends from Bethnal Green and married a Dutch Isis fighter.
They had three children but all died, including a baby boy born in the al-Hol camp earlier this year.
She gave birth days after being tracked down by Anthony Lloyd, war correspondent for The Times, and later gave interviews to other media outlets including ITN and Sky News.
She appealed to be allowed to return to the UK and claimed she was merely a “housewife”, but sources claimed she had been a member of Isis’s feared morality police.
A report released earlier this year by the UN Security Council warned that reductive “jihadi bride” stereotypes were causing female Isis members to be dangerously underestimated by security services.
It called on the UK and other member states to recognise the “many different roles, including as supporters, facilitators or perpetrators of terrorist acts” that women play, adding: “The gendered assumption that women lack agency can have serious security implications by letting dangerous actors slip through the cracks.”
The report said countries choosing to leave women in conflict zones “could exacerbate future Isis-related threats and, more generally, threaten the long-term recovery and stability of the region”.
Several British women became high-profile radicalisers, including the Scottish university student Aqsa Mahmood, who communicated with the Bethnal Green girls on Twitter before they left for Syria.
Ms Begum is among at least 20 British women and children being held in Syrian Democratic Forces camps after fleeing Isis territories, The Independent understands.
The black flag used by the terrorist group was raised to cheers at al-Hol four months after the territorial “caliphate” was declared defeated.