You would need to address the moisture problem and then repaint. Is there a leak behind the wall? from a roof or plumbing leak? Does the room not have good ventilation and the air is humid: consider things like putting a fan in the window to blow air in and exhaust old air out using a dual window fan. You can also run a dehumidifier to remove excess moisture. Putting an exhaust fan in the attic gable will also help cool the house and remove humid air.
Once you've address the moisture, knock off the paint flakes with a scraper or sander, prime and repaint.
The wall has to be completely dry before there would be any chance of getting the paint to stick. My guess is it needs damp proofing! Is it a basement room? Is the property rented and supposed to be for living accommodation? If so, get intouch with your Landlord and ask him to get the room Tanked as it could be bad for your health!
Find out what problem is then apply KILZ and paint over it