Members of Parliament
In formal address, the letters MP are always shown for a member of parliament.
They are shown seventh in the order of precedence of letters after the name, following: orders and decorations conferred by the Crown, Royal appointments, other appointments (Queen's Counsel, Justice of the Peace and Deputy Lieutenant) and university degrees. All letters after the name are preceded by the abbreviation Bt (Baronet) - if applicable - and Esq.
See Professions: Government/UK Parliament