Growing numbers of noncitizens, including legal immigrants, are held unnecessarily and transferred heedlessly in an expensive immigration detention system that denies many of them basic fairness, a bipartisan study group and a human rights organization concluded in reports released jointly on Wednesday.

Confirmation of some of their critical conclusions came separately from the Homeland Security Department’s inspector general, in an investigation that found detainee transfers by Immigration and Customs Enforcement were so haphazard that some detainees arrived at a new detention center without having been served a notice of why they were being held, or despite a high probability of being granted bond, or with pending criminal prosecutions or arrest warrants in the previous jurisdiction.

The bipartisan group, the Constitution Project, whose members include Asa Hutchinson, a former under secretary of homeland security, called for sweeping changes in agency policies and amendments to immigration law, including new access to government-appointed counsel for many of those facing deportation.

In its report, the human rights organization, Human Rights Watch, revealed government data showing 1.4 million detainee transfers from 1999 to 2008, most of them since 2006. The transfers are accelerating, the report found, with tens of thousands of longtime residents of cities like Philadelphia and Los Angeles being sent to remote immigration jails in Texas and Louisiana, far from legal counsel and the evidence that might help them win release.