Lambert told saintsfc.co.uk: "It is a disgrace of a decision, I have got to say.
"You can understand two or three yards but five or six - it's unbelievable. I haven't got words for it.
"It absolutely killed us going into half-time. At 1-1 at half-time at this place, it gives everyone a lift.
"We're not saying we would have drawn or won, but it would have been a different game. Going back out at 3-1 down, it's hard to get back into a game."