Ambrose moved close to locking up back to back series titles as he extended his points lead by finishing second in the round, but his achievement was overshadowed by a war of words and a $10,000 stewards' fine.
Holden teammates Rick Kelly and round winner Greg Murphy accused Ambrose of endangering Kelly and verbally abusing him after Saturday's opening race.
The bad feeling spilled over into a slanging match between Murphy and Ambrose in today's post-race press conference, with the Holden driver grilling his Ford rival and accusing him of not being truthful over what happened.
Kelly and Murphy claimed Ambrose deliberately slammed on his brakes as they crossed the finish line while Kelly was trailing him, forcing the Holden driver to take evasive action to avoid crashing into Ambrose's Falcon.
The manoeuvre, known as "brake-testing", is considered dangerous and unsportsmanlike in motor racing.
Ambrose today refuted both claims.
But stewards saw it differently, fining Ambrose $10,000 tonight for careless driving over the "brake-testing" incident and opening an inquiry over the abuse claims to be heard prior to the next round in Tasmania next month.
As Ambrose was denying any wrongdoing at the press conference, Murphy began asking him a series of questions about whether he'd slammed on the brakes or not.
A clearly rattled Ambrose accused Murphy of "ranting" and told the assembled media the way the Kiwi driver was behaving was "a joke".
Ambrose did admit to "slowing down" and also to saying something to Kelly in pit lane, though he denied it was abusive.
"I believe that Rick was out of line when he was a lap down, I'm trying to let him pass, and he refused to do so," Ambrose said.
"I was upset with him and I told him I was upset with him. That's all there is to it.
"I braked at approximately half normal pressure."
Murphy said he saw both incidents first-hand and had seen Ambrose hit the brakes hard and also abuse his teammate.
"It makes me angry that he's trying to get out of it â€“ making out he's goody-two-shoes when he's not," Murphy said.
"I heard what was said in pit lane and it wasn't what Marcos said it was, believe me."