that will never do!

that will never do!

That is completely wrong! That is totally unacceptable! Let me see how you're doing with the stitchwork there, John. Oh my, that will never do! I'm afraid you'll have to start over. You threw a tantrum in the market? Well, I'm afraid that will never do!
See also: never, that, will
Farlex Dictionary of Idioms.
See also:
  • it/that will never do
  • it/that won't do
  • I'll try (one) later
  • a run on (something)
  • a rush on (something)
  • I'm a Dutchman
  • at a loss, to be
  • be at a loss
  • ask (something) of
  • ask of