Mold is usually caused by poor ventilation, which would be a condition caused by the tenant not the landlord.
If you dont think its poor ventilation you could contact the Environmental Health Dept at your local Council and ask them to have a look, but do try extra ventilation first, especially in a bathroom or kitchen.
It's okay if your landlord is refusing to do anything. You can take a mold investigation test by the professionals and get sorted out with this problem.
Mold is also responsible for causing a number of health issues, so you can't avoid this problem.
You need to know which type of mold your flat is having. Some molds cause normal health issues, whereas others cause fatal effects.
To know more, you can visit http://www.moldtestusa.com/.