West Ham United manager Nuno Espirito Santo says players are confused about how much contact they can make while defending corners and said rules need to be clarified.
His struggling side twice led at home against Brighton & Hove Albion only to draw 2-2 and it could have been worse had Danny Welbeck's second penalty of the night not hit the bar.
Welbeck equalised from the spot and three minutes later was handed the chance to put his side ahead after what can only be described as a rugby tackle by Lucas Paqueta on Lewis Dunk.
Grappling and shirt pulling in the penalty area at corners has become a common occurrence in recent seasons but rarely do referees punish offenders.
Paqueta's action anywhere else on the pitch would have been an obvious foul and possibly a card but Espirito Santo appeared to question whether it should have been a penalty at all.
"I was talking to the referee because there are a lot of circumstances happening this season that many times they don't judge or whistle, so it's get confusing for the players. How excessive the contact can be or not," the Portuguese said.
"We arrive at a situation that it's difficult for players to judge how far they can go. I am disappointed to concede from a set piece because in that moment of the game we had it.
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"The referees must be clear, we had a meeting with PGMOL at the start of the season. Now, at halfway they should do it again to speak with the players."
Paqueta restored West Ham's lead from the penalty spot after Callum Wilson's shot was blocked by Dunk's arm but Brighton levelled after the break through Joel Veltman and the visitors dominated thereafter and should have taken three points.
West Ham are without a win in eight Premier League matches and remain third from bottom, four points from the safety zone at the season's halfway point.