ならともかく

ならともかく means "if it were X, fine, but…": it sets one case aside as acceptable and says the case at hand is not. It follows a noun or な-adjective directly, or a plain-form verb or い-adjective, sometimes with の in between: しらない知らないのならともかく.

The first case is the easy one – a child, a beginner, a small amount – and the second half is usually a criticism or a complaint. It can also be plain advice for a situation that differs from the usual.

ならともかく or はともかく

ともかく alone means "anyway", "setting aside". はともかく sets X aside without judging it: "X aside, Y". ならともかく adds "if": X would be acceptable, and the real case isn't.

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ならともかく works in conversation and in writing. ならまだしも is close in meaning with a sharper complaint, and ならいざしら知らず is the formal, written equivalent.