The Cherries boss slammed the decision not to overturn the decision to award the Bees a first-half penalty as “scandalous”, with Ivan Toney appearing to hold onto Marcos Sensei’s arm before the Argentine brought the striker down in the box.
Jarred Gillett’s on-field decision stood and Toney rolled in his 13th goal of the season before Mathias Jensen added a second to take Brentford up to eighth.
“Ivan Toney has managed to lock Marcos’ arm under him and pulled him down,” raged O’Neil.
“In this day and age with VAR it’s scandalous. I’ve spoken to the referee and told him I expect an apology.
“When I watched it I thought, ‘They’re definitely overturning that’. I thought it was a terrible decision.”
Still, speaking after Brentford’s third straight win, Frank replied: “I think scandalous is a big word to use. I’d be disappointed with my defenders if they defended like that.”
Brentford are back in action away at Leeds on Sunday.