Arsene Wenger believes Arsenal should “100 per cent” have been given a penalty during Monday's goalless draw with Chelsea at the Emirates Stadium.
Winger Theo Walcott appeared to be felled in the box by Willian in the 36th minute but appeals from Gunners players were turned down by referee Mike Dean.
And Wenger believes that his side were denied a clear and crucial decision against Jose Mourinho's men, which would have turned a tight game.
Arsenal are 5/1 with BetVictor to win the title this season
When asked why it had not been given, the Frenchman added: "That's a question you have to ask the referee, I cannot give it.
"In my mind there is no doubt."
The Gunners go into their Boxing Day clash with West Ham second in the Premier League, as Liverpool top the table on goal difference.
But Wenger is adamant that his side deserved the three points against Jose Mourinho’s Blues.
"I think in the final part of the game we should have won it. They came here to defend well and catch us on the break," the Frenchman added.
“We were a bit - you could see at the start of the game - a bit edgy, and when we took control of the game in the second half we should have won it.
"It was a game of very few chances and the few opportunities we had we couldn't take. When you cannot win the game, don't lose it and that's what we did."