The High Court, which has turned down his extradition challenges, decided the case did not raise ''points of law of general public importance'' - a prerequisite of being able to pursue a case at the higher level.

Mr McKinnon's lawyers said they would now consider applying the European Court of Human Rights in Strasbourg.

They argue that extraditing the 43-year-old, who suffers from Asperger's Syndrome and says his hacking was aimed at nothing more than searching for reports of UFO sightings, would lead to ''disastrous consequences'' for his health, including possible psychosis and suicide

Mr McKinnon, from Wood Green, north London, had challenged Home Office decisions allowing his extradition to go ahead and the refusal of Keir Starmer QC, the Director of Public Prosecutions, to put him on trial in the UK on charges of computer misuse. A UK trial would allow him to avoid extradition.

Gary McKinnon's mother Janis Sharp said after the decision: "No other country in the world would so readily offer its citizens to the US as sacrificial lambs merely to safeguard a 'special political relationship'.

"To use my desperately vulnerable son in this way is despicable, immoral and devoid of humanity."

Ms Sharp added: "Gordon Brown and Alan Johnson should hang their heads in shame - the judges are only interpreting the law before them, but this Government made the abhorrent law that brought about this situation.

"They could redeem themselves by taking a brave and principled stand by intervening now before it's too late.

"What Gary did was wrong, born of his compulsive and obsessive behaviour. But it does not justify Gary's extradition, which would be a cruel and excessive punishment, particularly given his Aspergers.

"I've fought for five years to protect my son and I am not about to give up now.

"I will stop this if it's the last thing I do. I will not stand by and watch Gary be destroyed, nor others like him who desperately need support, not injustice."

Mr McKinnon's solicitor Karen Todner said: "The effects of these proceedings on Gary have been devastating.

"The legal team are now considering our position and we will exhaust every avenue to prevent Gary's extradition."

Trudie Styler, a long-standing supporter of Mr McKinnon, said: "I implore this Government to show compassion and understanding towards Gary - a harmless, misguided and vulnerable man.

"Now is the time to put an end to his mental anguish and work with the US administration to prosecute him in this country. Anything less would be a dereliction of their duties."

The Home Office said no further comment would be made while Mr McKinnon continued to pursue the legal avenues available to him.

A spokesman said: "We note today's judgment. The case remains before the courts. Therefore, we do not propose to comment further at this stage."