Snitchiface

This phrase is used in the UK and Australia to describe someone that is rude or naughty. It's used by parents to tell their kids they are naughty when they really want to say a**hole or s***head for the action the kid has done. This can also be used in an office style environment as it is not considered a swear word.
In addition you can shorten it to snitch and then also use it in replace of saying bitch. Naughty words made polite. This was invented by an excellent Dad and it caught on and is used in all good neighbourhoods.

"You are a snitchiface" or "You have been a total snitchiface", and "you are a snitch".