The UK government has turned down a call to posthumously pardon Alan Turing.

A petition to pardon the war-time codebreaker for a 'gross indecency' conviction attracted more than 23,000 signatures, prompting the tabling of early day motion in the House of Commons last week.

Turing was arrested and eventually convicted for homosexuality in 1952. The conviction meant he was no longer allowed clearance to work on secret government projects. In addition he was forced to undergo a degrading hormone injection programme (chemical castration) as an alternative to a prison sentence. Turing spiralled into depression and ultimately took his own life two years later, in 1954.

Three years ago, former UK prime minister Gordon Brown issued an apology for government's treatment of Turing, describing it as "horrifying" and "utterly unfair" as well as praising Turing's outstanding contribution to the war effort. The apology fell short of the criminal pardon that some - but not John Graham-Cumming, the British programmer behind the 2009 Alan Turing apology campaign – had wanted.

However when the issue of granting a posthumous pardon was raised in the House of Lords a government minister said the option had already been considered and rejected at the time of the 2009 apology. Lord Sharkey said that even though Turing had been "convicted of an offence which now seems both cruel and absurd", a pardon is not appropriate because he was found guilty of something that was a criminal offence at the time.

Lord Sharkey's reply can be found on TheyWorkforYou here. ®