A Nigerian man said to be "near death" following a hunger strike is back in the UK after the Home Office flight deporting him had to turn around.
Lawyers for Isa Muazu, who has refused food for "over 100 days", said he was back at Harmondsworth detention centre.
It is thought the Nigerian authorities did not clear the plane to land.
Mr Muazu sought asylum in the UK saying he would be killed by Islamic extremists back in Nigeria. Labour said the government had questions to answer.
The Home Office rejects his arguments and attempted to deport the 45-year-old on Friday after he lost a series of legal challenges.
The privately-chartered jet carrying Mr Muazu was in the air for a number of hours, but it is believed the Nigerian authorities did not give the pilot landing rights. It is unclear why.
The plane is thought to have stopped in Malta for two hours before returning to the UK.
His lawyers say he has returned to the medical wing at Harmondsworth.
The Home Office refused to comment on the latest developments, but it is understood officials are working with the Nigerian government to try to secure Mr Muazu's removal.
He has been held in detention since he claimed asylum in July, saying he faced persecution from the hardline Islamic group Boko Haram.
Mr Muazu entered the country on a visitor's visa in July 2007 and stayed without permission after it expired in January 2008.
It is believed he then found work in south-east London and was detained on the day he claimed asylum, 25 July this year.
Duncan Lewis Solicitors, representing Mr Muazu, said his case was then fast-tracked and his application was rejected in August.
They said he had made himself "seriously ill" in his protest, adding: "His hunger strike lasted for over 100 days".
A claim that his detention was unlawful was rejected by the Court of Appeal on 25 November, and two further last-minute appeals were also refused, his lawyers said.
Shadow immigration minister David Hanson said Home Secretary Theresa May needed to "explain how this case has been handled".
"How could the Home Office put a man in this medical condition on a long flight at taxpayers' expense with no agreement from anyone that the plane could actually land?
"Deportations should be carried out with competence and humanity - neither of those things seem to have happened in this case."
And Lord Roberts, a Lib Dem peer, told the Observer newspaper he had seen Mr Muazu on Tuesday "when a doctor had judged him too ill to fly".
"Goodness knows what state he must be in now, the poor man," the peer said. "He needs hospital treatment.
"[Home Secretary Theresa May] has caused immense harm to one individual and spent an extraordinary amount of taxpayers' money.
"I hope there will be no question of sending this poor man away again."
The paper says when the plane landed he was "was taken off by stretcher".
The Nigerian is 5ft 11in (1.8m) tall, weighs eight stone (53kg) and has described himself as "looking like a skeleton", his lawyers have said.
He has said that he came to the UK "for a better life" and would "rather die" than face removal.