Akademik

не скажите
НЕ СКАЖИ(ТЕ) coll
[indep. sent; these forms only]
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(used to express an objection to or disagreement with what the interlocutor has said) you are not quite correct:
- I don't know about that;
- I'm not (so) sure (about that);
- I wouldn't be so sure (about that);
- don't be so sure;
- I wouldn't say that.
     ♦ Заговорили о немцах... "У них в общем [патрульные] пары не так крепки". - "Ну, не скажи" (Гроссман 2). The conversation turned to the Germans. ..."Their patrols don't stick together like we do." "I don't know about that" (2a).
     ♦ [Лукашин:] Ну, а я представитель самой консервативной профессии. [Надя:] Не скажите. Мы с вами можем соревноваться (Брагинский и Рязанов 1). [L.:] Well, I'm a member of the most conservative profession there is. [N.:] Don't be so sure. We can offer you some competition there (1a).

Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. . 2004.