Vulnerable migrants were forced to sleep in cold double-decker buses parked outside a processing centre.
The revelation comes in a shocking new report into conditions at a site at Dover.
The Tug Haven centre was so overcrowded, detainees slept on board the buses normally used for rail replacement services.
Some, including kids, were also told to sleep in small tents in freezing conditions.
Campaigner Clare Moseley, founder of charity Care4Calais, said: “No one in the UK should be sleeping on buses or in tents.”
The Tug Haven centre was set up to photograph and question asylum seekers who had crossed the Channel. It shut in mid-January.
The centre has since been replaced by a facility at the Dover port and a second 20 miles away at Manston, Kent. The report by said of its inspection: “Sleeping conditions were extremely crowded and the facilities were deemed far too small.
“During this period, those detained slept on thin foam mats... packed so closely together that there was no space between mats and people were practically touching.
“Some detained people slept on double-decker buses. There were also concerns about the temperature on the double-decker buses sometimes used for sleeping.”
Jude Clarke, of the Migrant Help, said: “Everybody deserves to feel safe and have their human rights protected.”
A government official said: “Since the inspection improvements have been made.”
