Al Bangura is appealing against the decision to refuse him asylum.
The Watford midfielder has been in the UK since 2003 after he escaped war-torn Sierra Leone.
Bangura had previously been granted asylum - but the Home Office said his status changed when he turned 18 and have been looking to deport him.
The Home Office contacted Bangura on Monday to inform him of their latest decision, but his guardian and advisor Tony Finnigan insists the fight is continuing.
"We received a letter from the Home Office on Monday, he now has ten days to appeal and that is exactly what we are going to do," Finnigan told skysports.com.
"We remain confident that justice will be done and Al will be allowed to stay in Britain.
"His MP has taken on the case and she has said she will take it to the Home Secretary - which we hope will have some impact."
Watford confirmed they would continue to back the 19-year-old in his bid to remain in the country.
"This is terrible news for Al and a big shock to everyone at Watford FC," said Iain Moody, head of football operations at Vicarage Road.
"We are very sad and disappointed that he has not been granted leave to remain in the UK."