The authorities must be allowed to deport failed asylum seekers, Nick Clegg has insisted after the Government spent thousands of pounds attempting to send hunger-striking Isa Muaza to Nigeria only for him to be turned away.
The Deputy Prime Minister said that the asylum system should be "fair and compassionate" to those in genuine need but promised to defend the principle that those whose applications are unsuccessful should be sent back to their home countries.
Mr Muaza, who has refused almost all food for more than three months and is said to be near death, was flown out of the UK on Friday after a last-ditch legal challenge failed.
But he had to be brought back via Malta when Nigerian authorities apparently refused the chartered plane permission to land.
Mr Clegg, speaking on a visit to businesses in Chiswick, west London, said: " I'm not going to provide a running commentary on one individual case. My understanding is that he has exhausted all the legitimate legal steps available to him to appeal against his deportation.
"But of course if you have an immigration system in which the British public have confidence it must be fair and compassionate and we must abide by our international obligations to grant people asylum where they have come here as refugees.
"But we also have the right as a country to say to those who haven't succeeded in making their case: look it's time now for you to go back to your home country.
"That is a principle which most British people, most of the public, would accept that we need to defend."
Mr Muaza, a 47-year-old from Maiduguri in the north east of Nigeria, entered the UK in July 2007 on a visitor's visa but did not leave when it expired.
After being detained for removal as an overstayer, he claimed asylum on the grounds that members of hardline Islamist group Boko Haram wanted to kill him. He says two members of his family have been murdered by the group.
The claim was rejected as "manifestly unfounded" in August, prompting his hunger strike.
Toufique Hossain, Mr Muaza's solicitor, told The Independent: "It is quite clear that the Home Office has taken a decision to get my client out of this country as soon as possible, even taking the highly unusual decision to hire a private aircraft to do so.
"Now after what has happened, he is an extremely distressed man. When he boarded that plane on Friday he thought that was it - the doors were locked and he genuinely believes he will be persecuted upon his return. We are now looking at our options to stop what is going on."
He s aid: "Theresa May needs 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."
A Home Office spokesman said: "We do not routinely comment on individual cases."