Nine-man Liverpool fell to an agonising late loss after Curtis Jones and Diogo Jota were sent off by referee Simon Hooper.
But things could have been different had Diaz's 33rd minute effort been allowed to stand at a time when Liverpool were a man down.
Instead, Son Heung-Min gave Spurs the lead and even though Cody Gakpo equalised for the visitors on the stroke of half time, Joel Matip put through his own net with virtually the last kick of the game in the second half.
England's referees organisation have now admitted that Liverpool were hard done by when Diaz found the back of the net.
“PGMOL acknowledge a significant human error occurred during the first half of Tottenham Hotspur v Liverpool,” a PGMOL statement read.
“The goal by Luis Diaz was disallowed for offside by the on-field team of match officials.
“This was a clear and obvious factual error and should have resulted in the goal being awarded through VAR intervention, however, the VAR failed to intervene.
“PGMOL will conduct a full review into the circumstances which led to the error.”
Liverpool's defeat was their first in the Premier League this season.
