The 19-year-old, known only as Stephen to protect his real identity, was forced to work in a cannabis factory when he was just ten-years-old.
Almost 120,000 people have signed a petition asking Home Secretary Amber Rudd to reconsider a decision by the Home Office that the Vietnamese boy should leave.
The Church of England has also rallied around the youngster, to support his appeal.
Stephen's foster carer Davina Tomlinson told Premier why she fears the "lovely" boy's deportation.
"If he goes back to Vietnam, he will be given £50 and the clothes he's wearing and as soon as he lands in Vietnam the police will pick him up and sell him on to a gang.
"Because he knows how to grow cannabis, he will be very valuable to them."
While the appeal in court was due to take place on Monday, Mrs Tomlinson informed Premier that the youngster's solicitor was told by the Home Office it would be postponed, as "new information has come to light".
It has not been confirmed when the appeal will take place and Mrs Tomlinson said the delay is "adding to the abuse that he's already suffered".
She added that it would be "heart-breaking" if he was sent away.
"He has nobody in Vietnam. He's made his life here.
"He's studying English at collage, he's been Student of the Year twice, he gives up two days a week to go and help students who aren't doing quite so well and who are new."
She urged people to be praying for Stephen.
"I'm praying the Home office will see sense and that they will grant him the right to remain - that he won't have to go through a court case with it all," she said.
"[I'm praying] that they will rethink their letter which is hopefully what the solicitor will be saying today... so if people can just really pray that justice will be done here - not just for Stephen but for other young people who have also been trafficked as well."
Listen to Davina Tomlinson speaking with Premier's Cara Bentley:
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