What has happened to good grammar?
"You are joking me" is grammatically incorrect. I cringe every time I hear some one say it, I dispair when I hear it on television, especially on the BBC. They should know better.

Joking is an intransitive verb and therefore should not be used in this way. It's as ridiculous as saying "you are laughing me". You can neither laugh me nor joke me. You can make a joke or say you are joking but please do not use "joking me".