Sajid Masih, 24, was being held along with his cousin Patras Masih, 17, for a Facebook post that insulted the Islamic prophet Muhammad.
Sajid, who is in hospital with critical injuries, said in a video recorded from his hospital bed that he was told to perform a sexual act on his cousin by police so jumped out of a window to get away.
Wilson Chowdhry, Chairman of the British Pakistani Christian Association (BPCA) told Premier the injured man desperately needs our prayers.
"There are fears that government agents... may cause something to happen within the hospital.
"We do need to pray for the man and for him to have a full recovery."
The cousins have insisted someone else posted the offensive content when the teenager's phone was stolen.
Hundreds of Christians in Pakistan fled their homes last week to escape riots in Lahore that erupted when locals became aware of the blasphemy allegations.
A protest will be taking place outside 10 Downing Street on Saturday calling for a full investigation into the attacks on the two men.
Listen to Wilson Chowdhry speaking to Premier's Alex Williams:
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