Accused NASA hacker Gary McKinnon has won the support of a key Parliamentary committee, which has called on the British government to block a request to extradite him to the US.

In a letter to Home Secretary Alan Johnson, the Home Affairs Committee said there was a "serious lack of equality" in the extradition treaty invoked in McKinnon's case. The missive came as Johnson's office is reviewing its authority to stop the forced transfer of the 34-year-old hacker, who suffers from Asperger's Syndrome.

"Because of Mr. McKinnon's precarious state of mental health, the committee is of the view that he should not be extradited to the USA and that you should exercise your discretion in this case," the letter, signed by committee chairman Keith Vaz, stated. It went on to say committee MPs had received "clear, legal opinion" from lawyers that Johnson had more authority in the case that the minister believed.

The letter called on Johnson to "comprehensively review" the controversial treaty.

Johnson's office issued a statement that largely rebuffed the committee.

"As the home secretary told the Home Affairs Select Committee on Tuesday, the evidence that must be provided for a US extradition request to proceed in the UK is in practice the same as for a UK request to proceed in the US," it stated. "The suggestion that the operation of the Extradition Act needs to be reviewed comprehensively is unnecessary."

The statement went on to say that the office had only limited discretion to deny the request.

"Unless the evidence shows that extradition would breach the European Convention on Human Rights it would be unlawful to refuse extradition," it stated.

The exchange follows a hearing earlier this week where McKinnon's mother told MPs her self-confessed hacker son would rather die than face extradition to the US for trial.

"We were told this treaty was to be used mainly for terrorists," she was quoted as saying. "People like Gary are not terrorists. We should stand up to America and say, 'This is wrong.'"

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