MK Dons manager Karl Robinson cut a frustrated figure after the 1-1 draw with Preston at stadium:mk in League One on Saturday.
Will Hayhurst scored from a tight angle in the seventh minute to cancel out Adam Chicksen's early opener for the Dons, who have now drawn four successive games.
Robinson said: "I don't think you can question the players' effort again.
"It's frustrating because I don't think you can say anyone shirked responsibility, they've all worked hard and I thought we deserved the win but one sloppy piece of defending has cost us."
Robinson then blasted the assistant referee for failing to spot what he felt should have been a penalty for his side when Dean Lewington went down in the area.
"We had one or two gilt-edged chances but there were two blatant penalties in there for us - it's remarkable how the linesman didn't see the Dean Lewington one," he added.
"The arrogance, ignorance and obnoxiousness of that man in front of me is beyond belief.
"I'll probably get fined for this but I don't care - he is one arrogant man and the way he conducted himself wasn't nice.
"The things he said, he shouldn't be an assistant referee.
"It's four draws now and we should have won them all but for some unknown reason it's just not happening. That was a very strong performance, I don't remember us really being under too much pressure in the whole game so it's frustrating. We're trying our best."