Sorry... I must have been unclear in my request. Again, I can do a choku-yaku myself -- I'm looking for an equivalent idiomatic expression that communicates the same concept as this English expression.
In English, this phrase describes "the huge problem of which we are all aware, but about which none of us are talking."
Though I'm not sure, I'm guessing that the equivalent Japanese phrase I'm looking for likely does not involve elephants or living rooms. ;-)