The Home Office explored the idea of buying the shipping container-style units as a way of cutting the £5million-a-day cost of keeping more than 40,000 asylum seekers in hotels.
There was a record 11,769 foreign national offenders out of prison but not deported at the end of September, Home Office figures show. The total was up by more than 800 in a year.
Each of the Home Office’s 1,000 asylum caseworkers reached just one decision a week. The backlog of cases awaiting an initial decision now stands at 122,000.