Asylum seekers who claimed they were assaulted by security staff hired by the Home Office did not have their complaints properly investigated, an official report has found.

Private security contractors involved in deportation also failed to properly manage the use of violent restraint techniques by their staff, it said.

The report was commissioned by ministers to examine claims of "systematic abuse" of 300 refugees made by campaigners against deportation and accused the Home Office of allowing "state-sanctioned violence".

Baroness Nuala O'Loan, the former Northern Ireland Police Ombudsman, examined in detail the claims made in the Outsourcing Abuse document which was published in July 2008.

In her 115-page report, she rejects the claim of systematic abuse and says the report actually contained only 48 individual cases. But she also uncovers a number of worrying cases and makes 22 recommendations for the UK Border Agency and its contractors.

Of 29 complaints she looked into, she found 18 where investigations were either inadequate or not carried out at all. In some cases staff had not even considered whether the use of force was "proportionate and necessary" when using force against refugees, she found.

Other cases could not be examined properly because they had been left in a rat-infested area and had become so contaminated they were a health risk.

Three cases resulted in serious injuries. They were a punctured lung, a broken finger and a dislocated knee.The review found "no satisfactory explanation" as to how the injuries happened in the first two cases. In the third, CCTV footage of the incident, which involved a violent struggle in the back of an escort van, was blocked by an escort officer standing in front of the lens.

But the report concluded there was no "pattern" of inappropriate force by any individual. It called for a review of how complaints are handled, better monitoring of complaints against individuals and a review of training on how force is used.

David Wood, strategic director of the Criminality and Detention Group at UK Border Agency, said: "We welcome the unequivocal findings of Baroness O'Loan that there is no evidence of systemic abuse by UK Border Agency escorts when removing individuals from the UK."