Referee Martin Atkinson pointed to the spot after Wojciech Szczesny challenged Ramires in the area, but replays showed that the Blues midfielder may have deliberately stuck out his leg in order to trip over the goalkeeper.
Frank Lampard’s converted spot kick ultimately proved decisive after Theo Walcott halved the deficit in the second half.
"I don't think it was a clear penalty. I think it was no penalty," the Arsenal manager told Sky Sports. "[The referee] could have given Ramires a yellow card. I didn't see it well from the bench but I've been told by people that have seen it on television that it is no penalty.
"If it's no penalty, it is no penalty. It's either a dive or the player has had to go down not to make contact. I don't know – all I've heard is that it doesn't look like a penalty on television."