It sounds obvious but the damp is coming from somewhere. Room above - guttering outside - condensation from inside - do you open a window when cooking or boiling? Could be a pin-hole in a pipe but even a tiny hole will soon have a small stream running down the wall and a puddle on the floor.
If the damp patches are all in the same localised area it may well be caused by moisture from an external source - is it a party wall to the house next door? If so what is the room used for - perhaps they have a leak? Are the damp patches restricted to a certain height either above or below a certain level? Are they in plain view or behind an appliance?
Most damp is caused by condensation - warm moist air against a cold surface - cure with better ventilation and a little bit of heating.
Richard Buxton
September 2008