Shamima Begum and her two friends were smuggled to Syria to join Isis by a Canadian spy, multiple reports have claimed.
The BBC has seen files which show he claimed to have shared Begum’s passport details with Canada, and smuggled other Brits to fight for the extremist group.
While a new book by former Sunday Times journalist Richard Kerbaj alleges that Canada asked the UK to cover up its role in smuggling the schoolgirls to Syria.
Both reports raise questions about whether Begum should have had her citizenship removed.
Begum was 15 when she travelled to Syria along with Amira Abase, also 15, and Kadiza Sultana, 16, fellow pupils at Bethnal Green Academy, east London, in 2015.
At the time, the extremist Islamist group was at the peak of its powers and controlled an area roughly the size of the Republic of Ireland across both Syria and Iraq.
British members of Isis - known as the Beatles - filmed themselves executing Western journalists and charity workers.
According to the BBC and The Times, Mohammed Al Rasheed, who is alleged to have been a double agent working for the Canadians, met the girls in Turkey before taking them to Syria in February 2015.
The three girls were at the centre of a mass public appeal to trace them, after the alarm was raised when they boarded a flight from Gatwick to Istanbul.
Kerbaj’s book - The Secret History of the Five Eyes - alleges that the Canadians were silent after the Met issued an urgent appeal to try and trace the schoolgirls.
It also claims that after Rasheed was arrested in Turkey later that year, Canadian Security Intelligence Service officers told Scotland Yard about their agents involvement.
A spokesman for the UK Government said: “It is our longstanding policy that we do not comment on operational intelligence or security matters.”
While the Met also declined to comment, saying: “We do not comment on matters relating to intelligence.”
In a forthcoming podcast for the BBC, called I’m Not A Monster, Ms Begum is quoted as saying: “He (Rasheed) organised the entire trip from Turkey to Syria… I don’t think anyone would have been able to make it to Syria without the help of smugglers.
“He had helped a lot of people come in… We were just doing everything he was telling us to do because he knew everything, we didn’t know anything.”
In February 2019, Ms Begum was found, nine months pregnant, in a Syrian refugee camp. Her British citizenship was revoked on national security grounds shortly afterwards.
She decided to challenge the Home Office’s decision to remove her British citizenship and wanted to be allowed to return to the UK to pursue her appeal.
In July 2020, the Court of Appeal ruled that “the only way in which she can have a fair and effective appeal is to be permitted to come into the United Kingdom to pursue her appeal”.
The Home Office challenged the decision at the Supreme Court four months later. The Supreme Court ruled in February 2021 that Ms Begum should not be granted leave to enter the UK to pursue her appeal.
Last summer, during an interview, Ms Begum said she wanted to be brought back to the UK to face charges and added in a direct appeal to the Prime Minister that she could be “an asset” in the fight against terror.
She added that she had been “groomed” to flee to Syria as a “dumb” and impressionable child.
Begum said she married Dutch convert Yago Riedijk 10 days after arriving in IS territory.
She previously told The Times that she left Raqqa in January 2017 with her husband but her children, a one-year-old girl and a three-month-old boy, had both died.
Her third child died in the al-Roj camp in March 2019, shortly after he was born.
The 23-year-old remains in a refugee camp in northern Syria, while Ms Sultana was reportedly killed in a Russian air raid and Ms Abase is missing.