VAR was employed on three occasions in the first half of the fourth-round contest, a 3-2 victory for the Baggies.
Almost four minutes elapsed between Liverpool’s Mohamed Salah being fouled and referee Craig Pawson awarding a penalty, which Roberto Firmino missed.
“FSF policy was always to back goal-line technology provided that the results were instantaneous and didn’t break the flow of the game. Clearly that didn’t happen on Saturday with VAR,” the group added in a statement to the Press Association.
Meanwhile, Reds manager Jurgen Klopp believes that the tie was cut short by six minutes following orders from broadcasters BT Sport.
“What I heard was that the actual extra time in the first half should have been 10 minutes,” said the German.
“It was only four minutes. I heard that television said it’s not longer than four minutes. Of course that’s not possible, you can’t cut match time because there is something else to broadcast.
“I don’t know what was on afterwards, maybe the news or something. It was 10 minutes and so you need to play 10 minutes longer.”
BT Sport said it had no influence on the amount of time added to a game.