new light trips when switched off

[nawd32]

fitted a double switch, from an existing light switch and added another light to the switch.
have a black wire left over from the new light socket to the old light socket. when this wire is connected to anything and turn switch off it trips the lights out. if this wire is not connected to anything the new light doesnt work, if it is connected then the light works, but when switched off, it trips out!!!
Any ideas, have searched similar topics and references to no avail!!

 

[Adam_151]

Draw us a diagram, your post is about as clear as mud...