I would say Parliament is a pretty good example of where there is a positive discrimination lobby. The main political parties are under a lot of pressure to ensure that there are equal numbers of male and female MPs, despite there being a smaller number of women being put forward for selection. Likewise, there is significant pressure to ensure equal numbers of men/women in cabinet positions, despite there being far fewer female MPs.
The result is a situation where women looking to get in to politics have a higher chance of success than their male counterparts.
Before someone misunderstands my point, I'm not suggesting that there shouldn't be roughly equal numbers of male and female MPs. I'm suggesting that the proportion should be roughly equal to the proportion of potential candidates and their experience. To achieve equality, a greater number of sufficiently experienced women should be encouraged to stand for selection, rather than treating the few that do with preferential opportunities.
I was reading about the Oldham by-election the other day, and one candidate for selection tried to infer that, were she not selected, that would demonstrate a prejudice against disabled, female single-parents. Needless to say, she wasn't selected, and has thrown her toys out of the pram about how the Labour leadership are discriminating against her. It's bizarre.