Gary McKinnon, the former hacker facing terror charges in the US for illegally accessing NASA and Pentagon systems, is likely to kill himself if extradited, according to a new report by psychiatrist Professor Jeremy Turk.

However, the Home Secretary has rejected an appeal from McKinnon’s lawyers to block extradition on grounds of mental health.

McKinnon has a “fixed-psychological conviction he will kill himself in preference to being extradited,” the report said, and his suicide is an “almost certain inevitability”.

Home Secretary Alan Johnson said that the information contained in the report was not “materially different from that placed before the High Court earlier this year”.

"His extradition to the United States must proceed forthwith,” Johnson wrote in a letter yesterday.

According to the Telegraph newspaper, he said that “should Mr McKinnon be extradited, charged and convicted in the US and seek repatriation to the UK to serve a custodial sentence, the Government will of course progress his application at the very earliest opportunity.”