Britain’s largest fostering charity has made an impassioned plea that the Parsons Green terror attack should not lead to a new crackdown on child refugees coming to Britain.

Eighteen-year-old Ahmed Hassan, who is believed to have arrived illegally in the UK two years ago as an orphan from Iraq, was charged with the terror attack that injured 30 people nine days ago on a rush-hour District line train.

Fostering and adoption agencies are worried that the government will use the bombing in west London as a pretext to stop child refugees being settled in the UK. In a letter to the children’s minister, Robert Goodwill, Tact Care’s chief executive, Andy Elvin, states: “Any attempted crackdown on child refugees would be wholly disproportionate to the evidence of potential risk.” The letter also claims that “by not accepting asylum seeking and refugee children in a planned way the Home Office are, inadvertently, increasing risks”.

Elvin said that security arrangements put in place in countries such as Greece were designed to ensure that potential terrorists were identified long before they could enter western Europe.

“If children and young people can be assessed in the camps and reception centres in southern Europe, then this information can be used by local authorities to match them with available foster and other placements in the UK,” he wrote. “If they have a family option here, the information can be used for local authorities to check that the relatives are suitable and able to offer care.

He also raises concerns that the government has made no attempt to “strongly refute” negative press coverage of foster parents and child refugees in the wake of the Parsons Green attack. “It should be noted that the overwhelming majority of recent terror attacks have been carried out by men born in the UK who grew up in their birth families,” said Elvin.

Hassan, who was stopped by Kent police near Dover a day after the attack, allegedly bought online the parts to make the improvised explosive device that was fillled with shrapnel.

Following the attack, police searched a home in Sunbury-on-Thames, Surrey, owned by foster parents Penelope and Ronald Jones, who are believed to have been looking after Hassan. Another refugee who had been looked after by the foster couple, a 21-year-old Syrian, Yahyah Farroukh, was released without charge last Thursday. Two other people, aged 25 and 30 respectively, remain in police custody in connection to the UK’s fifth terrorist attack of the year.

The debate on child refugees and terrorism has drawn fresh attention to the plight of unaccompanied minors in Europe at a time when dozens of young people in Greece have been left in limbo for more than a year after expecting to be admitted to the UK as part of the government’s commitment to helping Europe’s most vulnerable young refugees. Up to 60 children were expected to come to the UK under a scheme created by the Labour peer Alf Dubs, originally intended to resettle around 3,000 child refugees into the country. No unaccompanied minor has been transferred to the UK this year through the scheme, despite commitments by the government to house another 280 children.

On Friday, charities said they had identified 300 children in Greece who were eligible to be settled in Britain, but the vast majority had disappeared due to the UK government’s failure to act on the information. Lord Dubs visited Athens on Thursday to assess the situation.