focus changes to different windows

[Kritter]

I have Pidgin set up to open each new chat in a separate window. 
However, the when someone types something, the focus changes to that 
window regardless of where I select the focus to be.

SO let's say I'm chatting with Peter in window1 and John types something 
to me in window2, Pidgin switches the focus to that window and if I'm 
typing something to Peter, I now end up typing it in John's window instead.

How can I change it so that the focus remains on a specific window?

Thanks
Karl