Labour MP Andrew MacKinlay will not run at the next election after becoming disillusioned with the government over the extradition of Nasa hacker Gary McKinnon.
The Times reported on Friday that MacKinlay would step down after a vote to review the UK/US extradition treaty was supported by only ten MPs. Seventy-four MPs had previously expressed support for McKinnon's fight.
MacKinlay, who himself voted for a review of the law, blamed the influence of government whips on the poor turnout for the vote.
"In instances like the McKinnon case, which relate to people's rights and liberties as well as common sense, you should just spurn the diktats and the whips," MacKinlay told the Times.
Mr MacKinlay was not available for comment on Monday - parliament went into an extra-long summer recess on Friday. However, one of his consituency workers told ZDNet UK on Monday that MacKinley would be stepping down.
"He's going to retire," said the worker. "[The McKinnon case] is part of it, but at sixty years of age he's beginning to feel the job a bit."
Gary McKinnon stands accused of hacking into US Army, Navy, Air Force, Department of Defence, Pentagon, and Nasa computers in 2001. McKinnon, who says he was looking for evidence of UFOs when he accessed the systems, was diagnosed with Asperger's syndrome last August.
The UK/US extradition treaty was put up as a possible subject for parliamentary review, as from the ratification of the Extradition Act 2003 US prosecutors have not had to provide prima facie evidence of wrongdoing to secure the extradition of a UK citizen. The treaty is not reciprocal.