Labour has issued a stinging attack on Theresa May following the failed deportation of hunger-striking asylum seeker Isa Muazu.
The Nigerian was forcibly removed on Friday despite medical fears about his health, only for the plane to return to the UK after a 20-hour flight.
"Theresa May needs to explain how this case has been handled," shadow immigration minister David Hanson said.
"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."
Hanson's comments are the first major intervention from Labour in the Muazu case, following weeks of campaigning by human rights groups and parliamentarians.
May faces the prospect of being called before the Commons on Monday to explain why the flight returned to the UK.
Liberal Democrat MP Julian Huppert told Politics.co.uk he would be tabling an urgent question demanding answers about the deportation.
The home secretary insisted that she had been in contact with Nigerian officials on Thursday during a meeting with Lord Roberts of Llandudno, but just hours later the specially chartered flight carrying Muazu was understood to have been refused landing rights by the country.
Reports emerged of Muazu's return early yesterday morning, but lawyers asked for the news to be kept confidential in case media pressure triggered a new response from the Home Office.
The Home Office spent anywhere between £95,000 and £180,000 on the flight, after a previous deportation attempt on a scheduled Virgin Atlantic flight was cancelled.
May was already under pressure for the deportation, with doctors advising the Nigerian national was unfit to fly after having gone 90 days without food.
Muazu was unable to stand or see when he was deported from the UK.
Lawyers for Muazu also warned that the fast-tracking of his asylum case had failed to take proper account of the dangers he faced if returned to Nigeria.
Muazu says he will be targeted by Islamic terror group Boko Haram, which has already killed several members of his family.
The Home Office had previously exercised clemency in the cases of hunger strikers in immigration detention centres, but May redoubled her efforts in the case of Muazu by ignoring cross-party pleas for mercy and pressing ahead with the removal.
Muazu started eating again on his return to the UK. His lawyers are trying to secure a meeting with him today.
The Home Office says it does not comment on individual cases.