You can always rephrase the sentence from a negative to a positive, which will correct the behavior without sounding critical.
Train yourself to say what you want them to do instead of what you don’t. Notice the common element is starting with the word “you” and then acknowledging what they worked at, rather than what you think about it.
Kids hear the word “no” far too frequently (Read more about that here).
First, you are threatening a child, which makes them fearful of you.
Second, the threat is usually not something that is feasible to do (we are going home, you are going straight to bed, you don’t get dinner, you are grounded for a week, etc.) What we say in frustration is not only impractical but easily forgettable. You can train yourself to be clear and concise, using choices.
Choose whether the other person really needs to know about the issue, and if yes, let the child decide who will tell them.
“Do you choose to tell (Mom) what happened, or choose for me to tell her with you there to make sure that I explain it correctly?