The Home Office says it will change the way abuse allegations against immigration staff are handled following criticisms from a government watchdog.
The Border and Immigration Agency's Complaints Audit Committee said immigrants' and asylum seekers' complaints were often not followed up.
It found just 8% of complainants were interviewed and 89% of investigations were "neither balanced nor thorough".
The government promised a "radical, new complaints system" would be launched.
BBC home affairs editor Mark Easton said the committee had prepared the most critical report into the Home Office's work that he had seen.
There have been "glaring errors" in dealing with complaints about the treatment of immigrants being deported from the UK, the report says.
It criticises the denial of rights to those dealt with by private firms on behalf of the Immigration Service.
In 95% of cases, those investigating the complaints had been from the companies under investigation.
The report adds that "upwards of 20%" of records sought by the committee have been missing.
It said that 83% of replies received were "indefensible".
The committee's report, covering 2006/07, says investigations into misconduct complaints have been "poor".
There could only be a "most limited assurance on the quality and integrity of complaints management information we have audited", it adds.
Some 71% of misconduct complaints were not completed within time targets.
The report says serious misconduct complaints remain a source of "grave concern to us because of the risks of injury or death, wrongful arrest and civil liability arising from the arrest, detention and removal of failed asylum seekers".
Of those misconduct complaints received, 19% were over criminal behaviour - up from 12% in 2005/06.
Ram Gidoomal, one of the report's authors, told BBC Radio 4's Today programme that one of the most serious concerns was the lack of independent investigation.
The report's conclusion of widespread failings was a "very disappointing statement to be making in a report", he said.
But although there were "not lots of votes" in such issues, they needed to be tackled, he added.
"Human rights and justice are issues we should be very proud of."
One asylum seeker, Apollo Okello, told the BBC he had been bundled onto a plane at Heathrow and refused permission to see his lawyer, with the security guards knowing he already had permission to stay in the UK.
He struggled and was beaten up in the back of a van, he said.
He added: "That's where I was punched - my ribs, my eyes, my neck, my back."
One of the guards said "these black monkeys don't want to go back to their country", Mr Okello said.
In a statement, the Home Office said: "The Border and Immigration Agency has been actively working with the committee to design a radical, new complaints system which will come on line from February 2008."