Brushing off opposition anger, Prime Minister Shinzo Abe's ruling bloc on Wednesday rammed through an Upper House panel a contentious bill that in all likelihood will make Japan's arcane electoral system even more complicated.

At the heart of the controversy is a bill proposed by the ruling Liberal Democratic Party that will increase the number of Diet seats in the Upper House chamber — a move that flies in the face of a recent trend toward trimming them.

So what is the dispute over the bill and how would Japan's electoral system change?