The families of a group of Bethnal Green schoolgirls who went to Syria to join Islamic State have accused the Metropolitan police of Islamophobia over its handling of their cases.

The relatives – including those of Shamima Begum, the 19-year-old whose UK citizenship was revoked by the home secretary last week – were treated as suspects and were not privy to intelligence that may have prevented three of the eight girls reaching Syria, according to lawyers, a former senior Scotland Yard officer and community sources.

They claim that counter-terrorism officers were more interested in acquiring intelligence than fulfilling their duty of care and allege the Met also attempted to smear the reputations of some of the children.

Dal Babu, a former chief superintendent who has been instructed to speak on behalf of the families, has called for an investigation into what he says were serious cultural failings.

“There was a lot of Islamophobia. What happened was that they [the police] made assumptions. You had a police service with very little understanding of cultural issues, a failure to understand the Muslim community, a group of white men and women who, without understanding the community, decided what should happen and what shouldn’t,” said Babu.

Sharmeema Begum was the first of eight girls to travel from Bethnal Green Academy in east London to Syria in 2014. She was followed soon after by another who was removed by police from a plane readying for takeoff at Gatwick airport. Yet lawyers and community sources say the families of the other girls were not told about this development; if they had been, it may have prevented other teenagers leaving for Syria.

As it transpired, Shamima Begum, Amira Abase and Kadiza Sultana travelled to join Isis in February 2015. Another three girls were identified as being groomed to join the terrorist organisation. Community sources say they were made wards of court to prevent them leaving. “There was a decision not to share information with the families. There needs to be a serious case review into what happened,” said Babu, who was one of the country’s most senior Asian officers before he retired in 2013.

The Met said its primary focus was the girls’ safety and wellbeing and that it did not seek to criminalise them.

A community source said that when, in February 2015, the East London mosque asked worshippers to come forward with information about three missing schoolgirls, the Met already knew their whereabouts.

The police knew where Shamima Begum was, but did not share it with her family, according to a community source. Photograph: BBC News

“They didn’t disclose it to us or the families. They didn’t feel that the parents or the community could be trusted with that information. They were looking at it from the counter-terrorism viewpoint,” said a source.

They added: “The police were saying that they [the girls] stole jewellery from the families to sell it and pay for their travel but the families reported no jewellery stolen. They eventually stopped talking to the police because of the accusations and lack of apology.”

Shamima Begum’s family are exploring whether they can bring her baby son back to Britain as her lawyers begin a potentially lengthy appeal against the removal of her citizenship. She gave birth on 17 February in a refugee camp in northern Syria.

The mayor of London, Sadiq Khan, warned that the decision to strip her of her citizenship on the basis that she was of Bangladeshi heritage could have implications for millions of people who have family roots overseas. He said Sajid Javid, the home secretary, had created a second class of citizenship, with one tier protected and the other vulnerable to their rights being removed by the state.

Tasnime Akunjee, the family’s lawyer, told the Observer that the home secretary was attempting to export the UK government’s “hostile environment” policy. “It is shocking that he is exporting that policy and forcing a week-old British citizen abroad to remain in a hostile environment.”

New analysis by Global Future found that as many as 3 million British citizens, born in the UK, now in effect have second-tier citizenship, a figure that does not include another 7 million of Irish or Jewish descent.

Explaining the Met’s approach to the Bethnal Green case, Clarke Jarrett, head of its counter-terrorism command, said: “Our priority and focus from the moment the girls were reported missing was their safety and wellbeing. We were clear from the start that we wanted to try and stop the girls from reaching Syria, so that they could be returned safely home.”

He added: “This involved extensive and fast-time inquiries with the girls’ families and international partners to understand why and how the girls were travelling and give ourselves the best chance of finding them. As we said in 2015, our focus was not to criminalise anyone, but to prevent tragedies and support the girls and their families.”