truth be told

(idiomatic) Used when admitting something one might otherwise lie about, e.g. to keep up appearances or be polite. From "if the truth should be told".

Example:   I'm not sure if I can do this, truth be told.
  Actually, truth be told, I just don't like you.
2006, V For Vendetta (movie adaptation)
  Well, certainly there are those who are more responsible than others - and they will be held accountable - but again, truth be told, if you're looking for the guilty, you need only look into a mirror.