Migrants detained illegally, official email claims
The detention centres were used to hold about 450 people - described in one email as "overflow" from the migrant processing facility at Manston, Qazet.az reports.
The email said their detention was "no longer legal," adding: "We need to move them to hotels ASAP."
The Home Office said an unprecedented number of small boat arrivals had put "huge pressure" on the asylum system.
It said it had "worked tirelessly to move people into hotels or other accommodation as quickly as possible".
The email was sent on 4 November, the day after Home Secretary Suella Braverman visited Manston amid pressure to get a grip on overcrowding at the site.
According to a chain of emails, obtained under the Freedom of Information Act, the Home Office permanent secretaries - the department's most senior civil servants - were made aware of the concerns at the time.
Shadow home secretary Yvette Cooper said the emails "demonstrate the Home Office knew that they were breaking the law and lay bare how their chaotic failure to plan led to this situation".
"Under [Ms Braverman's] direction the Home Office has lost control of the system and has created potential substantial legal costs for the taxpayer."