Some private security staff who carry out immigration deportations are acting unprofessionally and continue to use control techniques that are likely to escalate difficult situations, the chief inspector of prisons has warned.

Nick Hardwick said that people deported from Britain were too often treated as "commodities to be delivered rather than as vulnerable individuals deserving of attention".

He also criticised the continued use of an "unacceptable" practice of taking other immigration detainees to the airport as "reserves" to be put on the flight if those already booked on it were unable to go. Hardwick said the practice "lacks humanity".

In an inspection report on a deportation of 66 migrants on a charter flight from Stansted to Islamabad, Pakistan, Hardwick said some Tascor private security staff made loud animal noises, swore loudly in front of deportees and fell asleep, despite being in charge of someone identified as at risk of self-harm.

Hardwick also expressed concern that the private security escorts knew little of the outcome of the inquiry into the death of Jimmy Mubenga while being restrained during a scheduled flight removal in 2010: "Escorts had still not been provided with training on the use of force in confined environments such as aircraft two-and-a-half years since inspectors first recommended it."

He said the deportation flight to Pakistan in December was well organised and completed with little incident, but too many of the inspection findings repeated those at previous inspections, particularly in relation to the dignity of detainees. The 124 Tascor employees on board the flight included a 10-strong security team, three healthcare staff and a chief immigration officer. The deportees were collected from four separate immigration removal centres and for some the journey lasted 18-and-a-half hours.

Despite being anxious and agitated, deportees were not told that the removal had been put back three hours, or that there was a further three-and-a-half hour delay before takeoff.

The inspectors said some staff were involved in successive removals with as little as 12 hours' rest between jobs, with the result that some had been at work for more than 20 hours by the time the deportees got off the plane in Islamabad.

"Some staff had fallen asleep as soon as they boarded the bus to the airport. During the flight, staff who were responsible for a detainee considered to be at risk of self-harm had also fallen asleep," said the inspection report.

The prison inspectors said their impression was that the vulnerabilities of deportees were not sufficiently central to the removal operation: "For example a few staff had conversations with each other over the heads of detainees, played with their mobile telephones on the coach, swore loudly or engaged in juvenile behaviour," they said, citing "making loud animal noises" as an example.

Deportees were referred to by passenger list numbers instead of their names and when they used the toilet on the coach or plane the door was wedged open with handcuffs.

Hardwick said: "Generally efficient procedures did not amount to respect for detainees who, it seemed to us, were seen as commodities to be delivered rather than as vulnerable individuals deserving of individual attention."

A Home Office spokesperson said they expected the highest levels of integrity and professionalism from their staff and contractors and took any allegations of inappropriate behaviour extremely seriously.

"We will carefully consider the report's recommendations and will respond formally as quickly as possible," he said.

"Those in the country illegally are given every opportunity to leave voluntarily and we offer them advice and support if they choose to do so. However, where individuals refuse to return by themselves, our only option is to enforce their removal.

"Any detainee placed on reserve for a charter flight removal is given 48 hours' notice and is kept informed throughout the process. This ensures removal flights are kept as full as possible minimising the amount of time detainees spend in detention."