Wales coach Warren Gatland claims the decision to disallow a Gareth Anscombe touchdown in the 12-6 defeat by England was a "terrible mistake."
Television match official Glenn Newman ruled Anthony Watson had beaten the Wales full-back to the ball during the first half at Twickenham.
But Gatland disagreed, saying: "It looked like a try to me.
"To me it's disappointing that they get the decision wrong and in such a pivotal moment of the game."
Gatland added: "They fly a guy over from New Zealand to be TMO and he has one big call to make and unfortunately I think he's made a terrible mistake and at this level I think that's pretty disappointing."
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England had established a 12-0 lead before the incident in the 23rd minute.
Referee Jerome Garces asked New Zealander Newman "try or no try" after Watson and Anscombe had dived on the loose ball in the England in-goal area.
After watching several replays, Newman replied "the first grounding was by England, therefore it is a scrum... no try."
A try would have made the score 12-5 with a conversion to come. Instead Wales managed two penalties as England produced a smothering defensive effort in the rest of the game to stop Wales scoring a try.
|What does law about grounding say?|
|A try is scored "by pressing down on the ball with a hand or hands, arm or arms, or the front of the player's body from waist to neck".|
|World Rugby law 21.1 b|
England coach Eddie Jones played down the incident.
"I'm sure Wales will claim they were unlucky, and maybe they were, but we have a TMO up there that makes the decision," he said.
"I don't make the decision, the TMO does."
Asked how big a turning point the decision was, Jones replied: "We don't know. It wasn't a try, so why speculate on it?
"We have a TMO up there to make the decision so I don't know why we debate the TMO's decision. He's got all the time in the world to make the decision and he makes it."
England are now unbeaten in 15 home matches under Eddie Jones and remain on course for a third successive Six Nations title after their fifth consecutive win over Wales.