Conditions in holding centres for immigration offenders awaiting deportation still need to be improved, the jails watchdog has said.
Chief Inspector of Prisons Anne Owers published reports on four immigration short-term holding facilities at Colnbrook near Heathrow Airport, Sandford House in Solihull, and Liverpool's Reliance House and John Lennon Airport.
Inspectors found that detainees at Colnbrook spent unacceptably long periods locked in single rooms, and there was a lack of information and independent advice for people facing removal.
But it had avoided some of the problems seen in other facilities because it was managed by the Immigration Removal Centre, offering access to healthcare facilities, welfare and race relations support, Ms Owers said.
Staff at the three centres in Liverpool and Solihull - all run by Group 4 Securicor - needed more training in the care and protection of children, her report found.
The facilities also required reorganising for a mixed population, it added.
Ms Owers said: "Accommodation still remains inadequate in many centres and the needs of detainees in relation to healthcare, information and advice, and preparations for release are not yet sufficiently met."
Home Office Minister Liam Byrne said: "I take very seriously the recommendations, and action plans responding in detail are currently being drawn up to ensure further improvements are made.
"It is important to remember that non-residential short-term holding facilities are intended to accommodate people for very brief periods of time."
Liberal Democrat home affairs spokesman Nick Clegg said: "The inspector's report confirms what has been apparent for some time: that, for the Government, these people are out of sight and out of mind.
"Any society should be ashamed when people are treated like this just because they are to be deported."
