I think it would not be right for someone to be excepting welfare and then have all this extra unused bedroom space at the same time. If a person is in need of welfare then he/she should make sure that he/she is not paying for something that they would not need first.
The bedroom tax only taxes spare rooms, and so helps the poor. It is designed to allow other poor to get rooms unused and un needed by welfare recipients. Labour is attacking the poor when it tries to abolish this tax, allowing one person to hog government housing all to themselves.