The following is the best answer to be found:
"Tip 2: Question of whether or question whether
A reader writes:
Just read this sentence in a legal text:
“Very often the question whether the particular conduct is within the scope of the consent . . .”
It caught my eye because I would write “Very often the question of whether the particular conduct is with the scope of the consent . . .” Or sometimes I might say “question as to whether”
And yet when I do, I’m always concerned that it doesn’t sound quite right.
Which is the correct way or are all three correct?
My first thought was that the reader was correct in his choices, and the quote was incorrect. Well, that’s why we use references—when I looked this up, I found that the quote was indeed correct. The reader was not incorrect in his alternatives, but the ‘of’ and ‘as to’ are not necessary to the meaning, and, as a general rule, we should get rid of any words that aren’t necessary. Garner calls ‘of’ and ‘as to’ in this context “minor prolixities.”
[NOTE: Prolixity is excessive wordiness.]
Fowler, never one to mince words, had this to say about ‘as to whether’:
…in such forms as Doubts are expressed as to whether, the ‘as to’ is not incorrect, but merely repulsive.
So let’s try to avoid being ‘merely repulsive,’ and omit the extraneous words.
And just as a reminder—we’ve talked about it before—‘whether’ contains an implicit ‘or not,’ so in most instances, ‘or not’ can be omitted.
Also, remember that when used in the idiom, ‘regardless of,’ the ‘of’ is not superfluous and must be used.
Regardless of whether the hypothesis is proven, the results should be interesting.
So, the question whether it is okay to say ‘question whether’ instead of ‘question of whether’ or ‘question as to whether’ is finally answered.
[NOTE: Gosh, it still sounds wrong to me, but, trust me, this is correct.]"