A Carmarthen schoolboy who lied about his past in a bid to get UK residency has apologised for deceiving his friends and foster family.
Pakistan-born Ahmer Rana won public support in a campaign against his deportation but now admits lying about his parents' death and his identity.
Mr Rana, real name Daniyal Shahzad, said he was under pressure to send money home to Pakistan.
The UK Border Agency said he failed to show he faced persecution in Pakistan.
Mr Shahzad said: "I'm really, really sorry. If I could go back and change everything, I would."
He added: "I know I let people down, people in school, my teachers, my friends and especially my foster family.
"My purpose was my family's future - I wanted a better life for myself and my brothers and sisters."
Mr Shahzad has lived in Wales since 2008, when he moved in with foster parents John and Lesley Hillard in Nantycaws, Carmarthen.
He was told by Home Office officials that once he turned 18, as he claimed last Christmas Day, he would have no right to remain in the UK.
He has since revealed he is in fact 19.
His earlier claims that he had no family in Pakistan and feared his missing parents were dead won huge public sympathy.
But his lies unravelled in the weeks after public supporters rallied round, travelling to London two days before Christmas to present a 4,000-signature petition against his deportation to the Home Office.
Mr Shahzad, a student at Queen Elizabeth High School, said the story began with one small lie to the Home Office when he arrived in the country four years ago.
He said: "I was young at that time. I was only 14 and I didn't know what was the best thing to do.
"I just came here to help my family. I was the eldest and thought I had a responsibility towards them.
"I started with a little lie and then built it up and made a big lie to cover my other lies but I'm really sorry about it."
His foster parents say they were "stunned" by the revelation but are sticking by him.
Mrs Hillard said: "I was very upset and depressed and wished he had told us and could trust us enough to speak to us about it.
"But he is from a different culture. We have children knowing that we want them, we don't put the responsibility of looking after us and our other children on the eldest child in the family.
"It's a big responsibility for a young man to have to shoulder."
Mr Shahzad said he was full of remorse for his actions but hoped he would be allowed to remain to complete his A levels.
He is awaiting an appeal against a judge who upheld the UK Border Agency's decision that he does not need the UK's protection.
A UK Border Agency spokesman said: "The UK Border Agency has fully considered Mr Rana's case and in an appeal hearing where his evidence was tested, a judge upheld our decision that he does not need the UK's protection.
"The judge found elements of Mr Rana's case were inconsistent and that he failed to show that he faces persecution in Pakistan. A further legal challenge has also been dismissed by the courts.
"Individuals like Mr Rana should leave the UK voluntarily when they have no legal basis to remain here, but if people defy the decisions of the courts we are left with no choice but to enforce their removal."
He added that Mr Rana's legal representatives are appealing against the judge's decision.
Nothing will happen to him until that appeal is heard.