Five senior mosque officials have been banned from office after management failures gave an extremist the opportunity to recruit a ‘children’s army’ of terrorists.

Umar Haque was jailed for life last year after using his position as a school administrator to show beheading videos to children as young as 11 as he tried to groom recruit them into a mini militia.

Haque, 25, worked at an Islamic private school and a mosque in east London, where he staged training exercises during Islamic studies classes to prepare children for ISIS-inspired attacks in London.

An inquiry into the charity that runs Ripple Road mosque in Barking, east London, found that the trustees failed to carry out proper background checks on Haque and then obstructed an inquiry by investigators.

Haque was taken on as an administrator but eventually led classes during his three years at the mosque - posting students as lookouts while he showed them the most extreme violence. He told his students that they should follow ISIS because one day the group would rule Europe.

Some 35 children have required long-term supervision as a result of the attempted indoctrination by Haque at the school and mosque, according to police. It emerged that he was working daily with children aged five to 15.

The grooming only came to light after Haque’s passport was revoked after he attempted to board a flight to Istanbul, with the apparent aim of joining ISIS. After his failure to fly to Syria, he turned his attentions to targets in the UK, including Heathrow Airport and mowing down pedestrians outside the UK parliament.

“We are a death squad sent by Allah and his messengers to avenge my brothers’ blood,” he told an accomplice during a conversation secretly recorded by police.

Michelle Russell, the director of investigators at the UK’s charity regulator, said it was the worst case of exposure to terrorist material that it had seen because of the trustees’ failure to supervise and manage Haque.

They initially claimed to have references for Haque, had done no due diligence on his background, and had not signed a contract – despite claims that they had done.

“In this case, the children who were in their care, and the people that trusted them to do so, were let down.

“These individuals proved themselves to be wholly unsuitable; what happened on their watch is deeply alarming and troubling, running counter to everything people expect of charity.”

A second man, Abuthaher Mamun, 19, helped Haque with his classes and was jailed for 12 years for his role in the terrorist plot. Charity regulators only found about Mamun’s role because of the trial and the charity trustees never told them about the role of Mamun at the school.

“It is not known why the former trustees failed to disclose this information to the inquiry,” it said.

The five trustees from the charity the Essex Islamic Acdemy, which runs the mosque, have been barred from holding any senior management positions in England and Wales for ten years. They have not been named.

The case highlighted the lack of effective scrutiny that allowed extremists to operate inside UK schools and mosques. The east London private school where Haque also worked was rated “outstanding” during the height of his activity in 2015.

The last inspection report in January this year downgraded the school to “inadequate” after discovering a book in its library that advocated death for anyone who committed adultery.