The House of Lords is a controversial thing. It is an unelected second house that is part of the legislative process in the UK. Seats are appointed, or in 26 cases given to senior Bishops in the Church of England. The senior Bishops are: The Archbishops of Canterbury and York and the Bishops of Durham, London and Winchester are the first five, the remaining seats are occupied by the longest serving bishops.
Most people outside of the UK who live in a secular society will probably think this is absolutely crazy, and they'd be right. Lords Reform has been on the agenda for some time, with promises of making it a democratic house being bandied around, as well as the notion of just getting rid of the thing entirely.
The most recent reform ideas contain controversy of their own. Although it proposes to basically half the number of bishops, it also reduces the number of Lords resulting in a net increase in the proportion of bishops to Lords (or rather Lords Spiritual to Lords Temporal). Other suugested ideas include getting rid of the privileged status of the CofE and having Lords Spiritual from other religious denominations (for instance, there are no representatives from the Church of Scotland, let alone any Imams at this time).
Most people who have thought seriously and read widely about the intersection of religion and politics will be able to anticipate the reasons for having Bishops given temporal power over legislation. Place your bets now...
The winner is: Bishops offer unique insight into ethical matters. Of course this reason is bollocks. I would suggest that dogma serves to blind Bishops of a range of ethical and moral considerations that makes them less insightful, not more. Take for example: assisted suicide for the terminally ill. Although most people (including the religious) in Britain are generally supportive of the idea given suitable protections etc, but bishops voted against it (the Lords as a whole did, in fairness).
The part that I find most shocking is that in the most recent Reform proposals the Bishops would find themselves exempt from the serious offence provisions. I cannot find details of what the serious offence provision is exactly, but it is proposed that instead of the procedure that applies to all other Lords, the Bishops will be expected to discipline their own. And we know how poor religious institutions are at doing that.