nothing could be further from my mind, the truth, etc.

ˌnothing could be ˌfurther from my ˈmind, the ˈtruth, etc.

used to emphasize that what somebody has said you are thinking is definitely not true: ‘You must be thinking how terrible I look.’ ‘Nothing could be further from my mind. You’re as beautiful as always.’People expect the richest people to be the most generous, but in fact nothing could be further from the truth.
See also: could, further, nothing