IPhone charging problems (charging is not supported with this accessory?)?

With my last iPhone one day when I tried to charge it it said charging is not supported with this accessory. At first i thought it was the charger and replaced it and everything was fine. Then it started happening again except it charged my phone but really slow and eventually my iPhone would say charging not supported with this accessory no matter what charger I used and I could barley charge it. Now with my new iPhone it's said it. Now I don't want to charge my iPhone for fear of restarting the Cycle. What could be causing this? Is this charger broken? Or could it be the outlet?

It usually happens to me too but not in a cycle, it happens if i don't plug the charger in properly or if the outlet is faulty. I use an apple charger in a 230V, 50Hz outlet.