Dozens of asylum-seeking children have been kidnapped by gangs from a Brighton hotel run by the Home Office in a pattern apparently being repeated across the south coast, an Observer investigation can reveal.

A whistleblower, who works for Home Office contractor Mitie, and child protection sources describe children being abducted off the street outside the hotel and bundled into cars.

“Children are literally being picked up from outside the building, disappearing and not being found. They’re being taken from the street by traffickers,” said the source.

It has also emerged that the Home Office was warned repeatedly by police that the vulnerable occupants of the hotel – asylum-seeking children who had recently arrived in the UK without parents or carers – would be targeted by criminal networks.