Home Secretary Theresa May has blocked the proposed extradition to the US of computer hacker Gary McKinnon, who has Asperger syndrome.

US authorities wanted to extradite McKinnon over offences relating to the hacking of government computers. McKinnon admits accessing the computers but has always claimed he was looking for evidence of UFOs.

However, May told MPs there was no doubt McKinnon was “seriously ill” and the extradition warrant against him should be withdrawn.

“After careful consideration of all of the relevant material I have concluded that Mr McKinnon's extradition would give rise to such a high risk of him ending his life that a decision to extradite would be incompatible with Mr McKinnon's human rights,” May said. “I have therefore withdrawn the extradition order against Mr McKinnon.”

But McKinnon may still face prosecution the UK. It is now up to the director of public prosecutions, Keir Starmer QC, to decide whether he should face trial.

McKinnon, who had faced the prospect of a sentence of up to 60 years in prison if he had been convicted in the US, had been fighting extradition since 2002.

Mark Lever, chief executive of The National Autistic Society (NAS), welcomed the Home Secretary’s decision: “We’re delighted that the years of waiting are finally over for Gary and his family.

“Janis’ [Sharp, McKinnon’s mother] relentless campaigning for her son and Gary’s stoicism in the face of some testing circumstances have been truly inspiring.

“People with Asperger syndrome can be vulnerable and the NAS argued long and hard for the Home Secretary to take Gary’s condition and its associated challenges into account when making this decision.

“A decade is a long time to wait, and those years can never be recovered but Mrs May’s decision has finally put an end to a difficult chapter.”