By Harriet Grant
BBC World Service
Torture survivors are not meant to be held in detention centres
Immigration minister Phil Woolas has admitted millions of pounds is being paid in compensation to migrants who have been detained in removal centres.
A Freedom of Information request to find out exactly how much was refused, but a BBC survey has found evidence of payments totalling at least £2m.
Five firms of solicitors say in the past three years they have won compensation for 121 individuals.
They say they have secured payouts of at least £1.7m from the Home Office.
That sum does not include costs.
Some of these were out-of-court settlements by the government, made without any admission of liability.
Other high-profile cases recently - including a Bolivian family who received £100,000 in January and a Congolese family paid £150,000 - bring the total to more than £2m.
Several more firms were unable to supply details of their cases because of confidentiality clauses in the compensation settlements.
In response, Mr Woolas said: "I suspect that's of the right order, but that is a fraction of the total number of cases we deal with."
Many of those given compensation were detained at immigration centres despite having evidence that they were torture survivors.
Every year, thousands of asylum seekers are held in centres while their claims are processed, a procedure known as the Detained Fast Track.
The government is moving towards processing 30% of claims in this way.
The Home Office's own guidelines say that people who have been tortured or are mentally unwell should not be detained unless there are exceptional circumstances.
But campaigners and lawyers who specialise in immigration say that screening procedures are failing to protect the vulnerable.
Mr F is from Uganda. He arrived in the UK with torture scars that are still visible today, but spent nine months in detention.
He was held in Harmondsworth detention centre, near London's Heathrow airport, and says his claim for asylum was refused without a doctor examining him.
"I told them I was tortured, but they didn't take it very seriously," he says.
"If you say you are tortured nobody cares. I was beaten, I was burned, plastic was melted on my chest and everywhere on my body."
While waiting to be removed from the UK, Mr F was examined by an independent doctor from the campaign group Medical Justice.
Dr Frank Arnold says Mr F's torture scars were very clear: "I found numerous scars, each highly consistent with the torture he described.
"Considered together, these and the psychological state indicated a very strong likelihood he'd been tortured in the ways he described."
Mr F was released following Dr Arnold's report. His claim for asylum is now being reprocessed and he has brought a civil claim against the government for unlawful detention.
Mr Woolas denied there were serious flaws in the screening process.
"We are not perfect, but we do provide medical assistance in our detention centres. People can also call in the experts," he said.
"If we do make mistakes, we put them right."
But barrister Stephanie Harrison disagrees. She specialises in unlawful detention cases and over the past two years has been involved in 100 of them, the vast majority of which have been successful.
She believes that detention in breach of the rules is institutionalised.
"The political calculation the government has made is that it's better to meet targets for removal than it is to avoid unlawful detention," she says.
But Mr Woolas stood by the checks and balances in the system and blamed lawyers for encouraging people to take legal action.
"I don't accept it's institutionalised. I think there is an inevitable problem of imperfection at the margin of the system and I think some lawyers have a self interest to highlight that because that's how they make their money."
You can hear the full investigation on Assignment, on the BBC World Service on 11 February