A Briton accused of hacking into US military and NASA computers on Friday lost his latest legal bid to avoid extradition to the United States.

Gary McKinnon, who suffers from a form of autism, could spend life in prison if convicted by a US court of gaining access to 97 computers in 2001 and 2002 in the aftermath of the September 11, 2001 attacks.

The 43-year-old, who now has 28 days to decide whether to appeal, says he was only looking for evidence of unidentified flying objects (UFOs) when he hacked into the US Navy and NASA space agency computers.

But the High Court on Friday rejected his lawyers' application for a judicial review of a decision last October by then home secretary Jacqui Smith to order his extradition.

"We are heartbroken. If the law says it's fair to destroy someone's life in this way then it's a bad law," said his mother Janis Sharp, standing outside the court after the ruling.

His lawyers had argued that he should not be extradited because he suffers from Asperger's Syndrome, a form of autism, and could commit suicide or suffer psychosis if extradited.

They say he could easily be prosecuted in Britain, where he would face a less severe sentence. But the Crown Prosecution Service (CPS) ruled in February that the case was best brought in the United States.

McKinnon's lawyers said Friday the legal battle is not over, pending a decision on whether to appeal. "This ruling is hugely disappointing. But we shall not stop here," said Karen Todner, one of his legal team.

"(Current Home Secretary) Alan Johnson still has the power to act. We have 28 days to review the judgment and will continue to explore every legal avenue until we achieve a just and proper result.

"The government promised 'ample protection' of individuals' rights, but we have yet to see this in practice. Extradition without effective safeguards is a denial of justice for every UK citizen," she added.

Trudie Styler, wife of rock star Sting and a supporter of McKinnon's cause, described the ruling as the "death of common sense'," adding: "I think every mother in England should write to Alan Johnson and say 'Use your common sense and have a heart'."

But Johnson insisted he has to abide by the law. "It would be illegal for me to stop the extradition of Gary McKinnon, which the court ruling has made clear," he said.

"Mr. McKinnon is accused of serious crimes and the US has a lawful right to seek his extradition, as we do when we wish to prosecute people who break our laws," he added, noting that McKinnon can appeal to the House of Lords.

Another lawyer for McKinnon said in June that Smith had not realised the severity of McKinnon's mental problems. "She underestimated the gravity of the situation," said Edward Fitzgerald.

British prosecutors have declined to begin proceedings against McKinnon, pending the US extradition request.

The National Autistic Society said it was "extremely disappointed" at the new decision. "We are angry that Gary is still in this position," said Amanda Batten, the charity's policy chief.

"This legal case has been going on for seven years. We are involved in supporting his case because we think that in the light of his Asperger's Syndrome that extradition should not go ahead.

"We will continue campaigning and do all we can to support Gary to stay in the UK."