Groups working with asylum-seekers say they are 'not surprised' by allegations of abuse of inmates by staff at a detention centre.
Evidence was gathered against Global Solutions Ltd staff at Oakington Immigration Reception Centre, near Cambridge, by BBC One's Real Story.
GSL says 15 people have been suspended from frontline duties.
A spokeswoman for the Refugee Council said the allegations showed detention should only be used as a "last resort".
"I think it does call into question the policy of systematically detaining people," said Refugee Council spokeswoman Hannah Ward.
"We would hope the government would look seriously at some of the alternatives to detention such as reporting procedures, where people are asked to report to the authorities on a weekly basis."
The BBC's undercover reporter heard evidence of detainees being physically and racially abused while officers made sure violence was not captured on CCTV.
GSL has said racism or abuse would not be tolerated and that an internal inquiry had been launched.
It said the majority of staff were "ordinary decent people doing a difficult job and they are feeling badly let down by a minority".
Edward Murphy of the Merseyside Refugee Support Network said the programme confirmed what they had heard before.
"It comports entirely with the accounts told to us by people who come out of these centres," he said.
Tauhid Pasha, for the Joint Council for the Welfare of Immigrants (JCWI), said: "We have dealt with one or two cases where detainees have alleged mistreatment at the hands of immigration officers so this type of situation doesn't entirely surprise us."
The documentary comes just months after an HM Prison Inspectorate report, based on a visit to Oakington in June, praised the "very good staff-detainee relations" and "caring and professional approach of most staff".
Hannah Ward of the Refugee Council said that was another cause for concern.
"We know Oakington is a relatively well-run centre according to the Chief Inspector of Prisons' report. So if this is happening there what's happening in other centres where the systems aren't so good?"
A Refugee Action spokesman, Stephen Rylance, said staff were "shocked and disturbed" by excerpts of the programme they had seen.
Mike Rahman of the National Union of Refugee Organisations, said the government needed to step in.
"They talk about terror but this shows detention is a form of terrorism where people who have come here to seek refuge are treated as criminals," he said.
Detention Undercover - The Real Story: BBC ONE, Wednesday 2 March, 2005 at 2100 GMT.