Dean pointed to the spot in the 89th minute after former Gunner Kieran Gibbs hit the ball at Calum Chambers' arm at point-blank range in the area. Jay Rodriguez levelled from the spot to cancel out Arsenal's lucky opener, when Alexis Sanchez's free kick was deflected into the net by James McClean.

While Arsenal were far from their best in the game, Wenger blasted the refereeing standards in England after the game and said the Premier League's scheduling was "completely unfair." Arsenal played Thursday night at Crystal Palace while West Brom played their previous game two days earlier on Boxing Day.

"It's disappointing to see that [penalty decision]. But what can you do? We can talk and talk and talk, it doesn't change anything," Wenger told Sky Sports. "And anyway, the Premier League doesn't face the problem.

"Not of the schedule, nor with the referees. I just would like to remind you that I did fight very hard with [former Arsenal vice-chairman] David Dean many years ago that the referees become professional. But their level, unfortunately, doesn't go up."

Goalkeeper Petr Cech was also uncharacteristically angry after the game, having been booked by Dean for protesting the penalty decision.

"The player is too close to the ball, he has no chance to react," Cech told Sky Sports. "That will never be a penalty. The referee gives this with two minutes to go, that's why I ask him: 'Why?' ... He could have told me. He just walked away and gave me a yellow card. I was not rude, I just asked a question. And I think this disappoints me even more. ... I expect when I walk toward a referee with respect and ask him a question, I would as well like that he answers to me in a normal way. Not gives me a yellow card and say nothing."

Wenger added that the result was "difficult to accept," and again called for video-assisted replays (VAR) to be introduced in the Premier League.

"It's time. I don't know why we want to be the best league in the world and we wait for such a long time and other leagues use it already," Wenger said. "But overall I believe the schedule is not right. West Brom has five days to prepare for a game like that, we have three. Chelsea has four days to prepare the game on Wednesday, we have three.

"And you can look since the start of the season, the Premier League has to become serious a little bit and look at how the schedule is fair or not fair. On our side it's completely unfair. ... If we play every day, I have no problem. If the team we play against has played the day before as well, I accept it completely. But the way they organise the schedule cannot be right. It's nothing to do with top-level sport."