I would also suggest that you copy This email address is being protected from spambots. You need JavaScript enabled to view it. In any correspondence to your local MP, Dr Therese Coffey is the Secretary of State for Work and Pensions and has overall responsibility.
Unfortunately some MP's are more pro-active than others, I would copy in Thérèse Coffey Secretary of State at the Department for Work and Pensions (This email address is being protected from spambots. You need JavaScript enabled to view it.) in any correspondence to your local MP as stated by Lindsey below.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems