By Alan Travis
Ministers have been warned by an official immigration watchdog of the "excessively long" periods, including cases of more than three years, that detainees are being held at Europe's largest removal centre.
A "snapshot" taken last December showed that 35 detainees at Harmondsworth removal centre, near Heathrow airport, had been waiting more than 12 months to be deported, including seven who had been waiting more than two years.
Harmondsworth's officially appointed independent monitoring board (IMB) said one man had been held in detention for three years and seven months at a cost of £110 a night. The bill is already more than £144,000.
"This is not only emotionally costly to detainees but expensive for the taxpayer," says the IMB's annual report to the immigration minister, Damian Green. It adds that the latest national figures show that as of 3 March, 170 detainees around the country have been held more than two years waiting for their removal.
The watchdog raises the problem of "hidden children" being held in immigration detention centres despite the coalition's pledge to end the practice. The IMB's annual report reveals that six children who were held last year at Harmondsworth were removed by social services when it had been established they were children.
The watchdog said they were part of the problem of young people being detained by the UK Border Agency as adults despite claiming to be under 18.
"Arrangements should be made for the rapid assessment of those claiming to be under 18," the IMB reported.
Harmondsworth, which is run by a US private security company, GEO, became the largest immigration detention centre in Europe last year when four prison-style wings were opened, trebling the total capacity to 615 people.
The report was published as a freedom of information request revealed a surge of complaints last year against the security company G4S over its running of four immigration removal centres. In 2010 the company received 773 complaints from detainees – 240 more than the previous year.
Nearly 130 of the complaints were fully or partially substantiated. Most concerned lost property, poor quality food or poor communication but 25 of the complaints that were substantiated involved the conduct of individual members of staff. They included two complaints of serious assault by staff on detainees at Harmondsworth and at Tinsley House, near Gatwick. A third case of assault at Harmondsworth is still being investigated.
G4S lost the contract to carry out immigration deportations last year. A police investigation continues into the case of Jimmy Mubenga, an Angolan who died after being restrained by three G4S guards on a flight.
A spokesman for G4S said:
"Anyone detained within our immigration facilities is given every opportunity to raise concerns about either the treatment they receive from our staff or the services we provide.
"The level of substantiated complaints against our employees over the last three years, at 25, is extremely low and of a minor nature, albeit we take each one very seriously.
"The vast majority of upheld complaints relate to issues at Brook House IRC, which houses some of the UK's most challenging detainees, including a number of convicted criminals, prior to their deportation."
David Wood, head of criminality and detention at the UK Border Agency, said:
"The way that complaints are processed and recorded has been made simpler in recent years, which has led to a rise in recording.
"Complaints range from issues about the food served at mealtimes to more serious issues. Importantly these figures show a decrease in substantiated complaints and that the majority of complaints are minor and relate to availability of facilities at the centres."