Computer hacker Gary McKinnon is "unable to control the terror that consumes his every waking moment" as he fights extradition to the US, his mother said.

Janis Sharp said the treatment of her son, who admits hacking into military computers but claims he was looking for evidence of UFOs, was "barbaric".

She met supporters outside Number 10 to hand over poems of support for her son to mark the 10th anniversary of his first arrest. She urged Prime Minister David Cameron to raise the issue with US president Barack Obama when the two leaders meet at the White House next month.

Ms Sharp said: "Ten years have gone by and still Gary lives in a nightmare world - unable to control the terror that consumes his every waking moment. This endless pressure on an Aspergic man with severe mental health issues is barbaric. And for what? A foolish act that caused embarrassment to the US. Where has our sense of proportion gone?"

She told reporters on Downing Street: "He can't deal with it. He sits in the dark - it's ruined his life. His mental health has deteriorated and it's ruined our lives." And Ms Sharp said her son does not have an outlet because he cannot use a computer.

The High Court expressed concern over how long McKinnon's case was taking to return to court last month, with two judges listing the case for July in a bid to speed matters up.

They acted after hearing that Home Secretary Theresa May is "considering afresh" whether Asperger's sufferer McKinnon should be extradited to the US to face trial for hacking into military computers in 2002.

She said: "In March David Cameron is visiting President Obama to discuss our 'special relationship'. What an opportunity for our PM to finally announce an end to Gary's 10-year ordeal. This act alone would prove that the 'special relationship' has true meaning and is one of mutual respect."

McKinnon's legal team hopes Mrs May will block extradition amid predictions he could be jailed for 60 years in America. Medical evidence shows the 45-year-old was "suffering from a serious mental disorder and there is a serious risk of suicide if extradited", his legal team has said.

McKinnon, from Wood Green, north London, admits hacking but claims he was looking for evidence of UFOs.