Michael Cheika believes referee Jerome Garces made it "impossible" for Australia to beat Ireland as their grand slam hopes were ended in Dublin.
The Wallabies fell to a 27-24 defeat despite fighting back from 17 points down to lead, leaving Cheika's hopes of ending a 32-year wait for a clean sweep in tatters.
But the Australia coach felt the referee made it difficult for his side, pointing to the penalty count as an indication of the poor officiating.
"I thought we played a lot of footie, but we got penalised a lot, didn't we," he told a post-match news conference.
"A 13-3 penalty count costs you field position, territory and then obviously points as well.
"You can't win a test match giving away that many penalties or [having] that big a difference between the two teams. [It is] impossible.
"It's something I will be dealing with [World Rugby referees' chief] Alain Rolland afterwards. He is the referee's boss so I'll go through the proper channels as opposed to making it an issue out here.
"And let's see if we can get something out of it - but I doubt it."
Australia travel to Twickenham to face England next weekend.