A Scottish UFO enthusiast accused of the "biggest military hack of all time" vowed to keep fighting extradition today despite unanimous defeat at Britain's top court.

A Scottish UFO enthusiast accused of the "biggest military hack of all time" vowed to keep fighting extradition today despite unanimous defeat at Britain's top court.

Gary McKinnon, an unemployed 42-year-old now living in north London, faces a lifetime in jail if convicted in the United States of sabotaging vital defence systems in the wake of 9/11.

Speaking after losing at the House of Lords - his final possible appeal in this country - McKinnon's legal team said their battle would carry on at the European Court.

McKinnon now has 14 days to appeal to the European Court. If a further hearing is granted McKinnon's extradition will be stopped until the European verdict.

His lawyers point out he could be sent to Guantanamo Bay as a terror suspect - despite his insistence that he accessed Pentagon computers looking for information about aliens.

A statement on McKinnon's behalf said: "The consequences he faces if extradited are both disproportionate and intolerable and we will be making an immediate application to the European Court to prevent his removal."

McKinnon - who used an online name of SOLO - was never charged in Britain after admitting accessing 97 US military and Nasa computers from the bedroom of his girlfriend's aunt's house in north London.

He always maintained he was motivated by curiosity and he managed to get into the networks only because of lax security.

But American authorities claim he stole 950 passwords and deleted files at Earle naval weapons station in New Jersey.

He was also charged with hacking into 16 Nasa computers and one US Defence Department computer.

McKinnon was traced in 2002 when he attempted to download an image he believed was an alien spacecraft from a Nasa computer.

He was warned by the US authorities he faced a life sentence rather than a couple of years in jail unless he agreed to plead guilty and accept extradition.

But the former systems analyst complained this was an abuse of the extradition process.

His appeal was dashed by Lord Brown, who gave the lead judgment of the unanimous ruling this morning.

Lord Brown said: "It is difficult, indeed, to think of anything other than the threat of unlawful action which could fairly be said so to imperil the integrity of the extradition process as to require the accused, notwithstanding his having resisted the undue pressure, to be discharged irrespective of the strength of the case against him."

The Law Lord said McKinnon used his computer via the internet to identify US government network computers with an open Microsoft Windows connection. The cost of repair was £450,000, he said.

Lord Brown said: "The appellant's conduct was alleged to be intentional and calculated to influence the US Government by intimidation and coercion. It damaged computers by impairing their integrity, availability and operation of programmes, systems, information and data, rendering them unreliable."

Speaking after the verdict, his lawyer, Kaun Todner, said: "Gary McKinnon is neither a terrorist, nor a terrorist sympathiser.

"His case could have been properly dealt with by our own prosecuting authorities.

"Instead, we believe that the British Government declined to prosecute him to enable the US Government to make an example of him.

"American officials involved in this case have stated that they want to see him 'fry'."

The latest defeat comes after McKinnon lost his case at the High Court last year.

His supporters say he is being made a "scapegoat" for security shortcomings on US military networks.

McKinnon previously described his exploits as "ridiculously" easy, saying: "I was amazed at the lack of security and the reason I left not just one note but multiple notes on multiple desktops was to say 'Look, this is ridiculous'.

"My intention was never to disrupt security. The fact that I logged on there and there were no passwords means that there was no security."

The Law Lords heard McKinnon admitted leaving a message on an army computer reading: "US foreign policy is akin to government-sponsored terrorism these days ... It was not a mistake that there was a huge security stand down on September 11 last year ... I am SOLO. I will continue to disrupt at the highest levels."

Home Office spokesperson said: "The House of Lords has today dismissed Gary McKinnon's appeal by which he sought to defeat the USA's request for his extradition.

"His solicitors have given notice of their intention to appeal further to the European Court of Human Rights (ECtHR) in Strasbourg "In these circumstances, the Home Secretary's policy is to allow the person 14 days in which to seek and obtain "interim relief" from Strasbourg.

"If granted, Gary McKinnon's surrender will be deferred pending the outcome of ECtHR consideration. If refused, arrangements for surrender to the USA will be put in hand."