MacBook Pro burnt wall plug pins

I recently got a new MacBook Pro (2015 model, i5, 8gb ram, 128gb ssd) and after charging it at home for the first time, I noticed that the live pin on the part of the plug that goes into the wall had a black burn mark on it. I immediately contacted Apple support and they sent me a new Magsfe and plug adapter, however this still caused the burning issue. Next I tried another 4 wall sockets in my house - with the new adapter - and each caused burn marks on the live or neutral pins.

So I then assumed the problem must be with the Mac itself and as I'd had it for less than 30 days I got a replacement from PC world. However to my sheer disbelief the problem happened with the plug again. So I took it to my grandmothers house (she lives out of town) but there it still happens and when I plugged it in there was a loud crack and a blue flash. So I have no idea what is causing the problem but every time I plug it in, either to a single socket or an extension lead there are burn marks. There is no smell of burning nor excess heat and it seems to charge normally.

Does anyone have any idea what is causing this?

Has anyone ever experienced anything like this? Apple seem just as confused as I am!