Imprisonment, after due legal process, as a sanction for those who break the law is acceptable as a practice in this country, and in any other country. Human rights principles, as expressed in the UN Declaration of Human Rights, in the European Convention on Human Rights and, indeed, in Catholic social teaching, put the emphasis on the existence of due process and rule of law to make this a right thing to do. The question of imprisonment, purely in itself, is not unethical.
Imprisonment involves the deprivation of a person's liberty; it involves a restriction of a person's "stake", of their participation in society, in most cases for a period of time before that restriction is then removed. My own view happens to be that imprisonment should have this effect of restricting, rather than removing completely, a person's participation in society. In practice, this implies that programmes of education, rehabilitation or personal development should be available during a prison sentence. Family and societal support should also be available. All of this being subject to a test of reasonableness and appropriateness to the prisoner's particular situation. One could argue that it is part of the agenda for social cohesion.
So the idea that prisoners should be able to vote, due to be debated in Parliament today, does not seem to me to be unreasonable.
My problem is with David Cameron's reported remark, being repeated on the radio today, that he feels "physcially ill" at the thought of giving convicted prisoners the right to vote. If he had made this remark about any other group in society, there would have been uproar. Why is there not uproar because it was made about prisoners?