Private security officers removing deportees from the UK showed "a shamefully unprofessional and derogatory attitude" which did not give confidence that any serious incidents would be dealt with effectively, inspectors have said.

Nick Hardwick, the chief inspector of prisons, said some staff showed an "unacceptably unprofessional attitude" and tensions were raised when force or restraint was used unnecessarily.

Some escorts spoke to detainees in patronising terms while others used "highly offensive and sometime racist language" between themselves, he said.

He added that it was a concern that inspectors needed to urge the UK Border Agency (UKBA) to ensure detainees "are treated decently at all times, with no physical or verbal abuse, throughout their journey and when they arrive".

The UKBA said it expected "the highest levels of integrity" from its staff and contractors, adding that "racist and unprofessional behaviour will not be tolerated".

The critical reports come after inspectors accompanied 104 staff who were escorting 35 detainees to Jamaica and 131 escorts who were removing 53 detainees to Lagos, Nigeria, in March and April this year respectively. They also reviewed records of previous removals. The flights were chartered by the UKBA and private security firm G4S provided the guards.

In his report on the flight to Nigeria, Mr Hardwick said that while most escorts worked in a calm and professional manner, "escorts sometimes spoke to detainees in patronising terms". "Inspectors were very concerned at the highly offensive and sometime racist language they heard staff use between themselves," he said.

One senior officer used "wholly unacceptable terms", including "gippos", "pikeys" and "typical Asians", to describe minority groups, he said. "This was not in the hearing of detainees, but it could be heard by other officers and communicated a disrespectful and racist attitude."

Jonathan Ellis, director of advocacy at the Refugee Council, said the report showed there was a clear case for a review of the removals process. He said: "It is unacceptable that people being returned to their own countries are not only still being forcibly restrained unnecessarily, but also have to put up with derogatory and offensive behaviour from their escorts."

Security firm G4S said it does not tolerate offensive and racist language among its staff. A spokeswoman said: "We are concerned by any suggestion that our staff were anything less than respectful to detainees and have received no complaints from the detainees on either of these flights."