Gary McKinnon will be extradited to the United States on computer hacking charges
Computer hacker Gary McKinnon could be sent to the US within weeks after the Home Secretary refused to block his extradition.
Alan Johnson finally dashed hopes that the Government would intervene in the case, insisting there was no evidence that the extradition would breach Mr McKinnon's human rights.
Mr McKinnon's mother, Janis Sharp, said ministers should "hang their heads in shame" for the "barbaric" decision.
His legal team is to apply for a judicial review within days, but Ms Sharp warned that if that was not granted then her son could be extradited by Christmas.
Mr McKinnon, who has Asperger's syndrome, faces up to 60 years in jail for hacking into Pentagon computers soon after the 9/11 terror attacks. He says he was looking for evidence of UFOs.
He and his family, who have led a high-profile campaign to block the extradition, were given hope last month when Mr Johnson agreed to study new medical evidence. The Home Secretary's deliberations came after the High Court refused the 43-year-old permission to appeal to the Supreme Court against his removal.
But Mr Johnson said in a statement: "I have carefully considered the representations in the case of Gary McKinnon. I am clear that the information is not materially different from that placed before the High Court earlier this year and does not demonstrate that sending Mr McKinnon to the United States would breach his human rights.
"As the courts have affirmed, I have no general discretion. If Mr McKinnon's human rights would be breached, I must stop the extradition. If they would not be breached, the extradition must go ahead."
Mr McKinnon's family say that his health has deteriorated significantly under the pressure of the pending extradition and fears about how he will be treated by the US authorities. There are fears that he may even commit suicide.
Ms Sharp said: "To force a peaceful, vulnerable, misguided UFO fanatic like Gary thousands of miles away from his much-needed support network is barbaric. This is a cruel and miserable decision. If the severity of Gary's medical condition isn't sufficient to prevent his extradition, I can't imagine what is. God help others facing a similar fate. I'm so upset and angry."