The fate of a male nurse who "is certain that if he returns he will be murdered" particularly concerned him, Firth told The Independent Monday.
The nurse fled the Democratic Republic of Congo five years ago after the assassination of former President Laurent Desire Kabila. He was working in the Congolese army as a nurse at a military hospital where captured officers were housed. After refusing to inject the prisoners with strong doses of morphine, "my life has been in danger," the nurse said.
Firth said he learned of the case through his mother, who is president of the Southampton and Winchester Visitors' Group, which offers asylum-seekers emotional and financial support.
"To me it's just basic civilization to help people. I find this incredibly painful to see how we dismiss the most desperate people in our society," Firth said.
A Home Office official declined to comment on individual cases.
Kate Middleton recycles dress at movie premiere
Jordana Brewster on Paul Walker: 'He was an enormous presence in my life'