https://www.theguardian.com/society/2017/oct/29/government-planning-to-allow-some-prisoners-to-vote-european-court-human-rights
If the voting rights remain limited to prisoners with less than a year to serve, then I have no real issue with it (although I do wonder why they can't wait a year), but if the year starts to creep to be two years, and then five and so on, I would object.
There's no suggestion the time period will be amended to include longer term prisoners, but purely for the sake of the argument if it was, I would struggle with the idea of allowing people who have chosen to live outside of society's rules have a say in electing people whose job it is to make those rules.