UK government minister, Lord McNally, responded for the government declining to pardon Turing:
The question of granting a posthumous pardon to Mr Turing was considered by the previous Government in 2009.
As a result of the previous campaign, the then Prime Minister Gordon Brown issued an unequivocal posthumous apology to Mr Turing on behalf of the Government, describing his treatment as "horrifying" and "utterly unfair". Mr Brown said the country owed him a huge debt. This apology was also shown at the end of the Channel 4 documentary celebrating Mr Turing’s life and achievements which was broadcast on 21 November 2011.
A posthumous pardon was not considered appropriate as Alan Turing was properly convicted of what at the time was a criminal offence. He would have known that his offence was against the law and that he would be prosecuted.
It is tragic that Alan Turing was convicted of an offence which now seems both cruel and absurd-particularly poignant given his outstanding contribution to the war effort. However, the law at the time required a prosecution and, as such, long-standing policy has been to accept that such convictions took place and, rather than trying to alter the historical context and to put right what cannot be put right, ensure instead that we never again return to those times.
via UK Government declines to pardon Alan Turing | John Graham-Cumming.