Swansea boss Paul Clement accused Marcus Rashford of "deceiving the referee" to win a penalty for Manchester United in Sunday's 1-1 draw at Old Trafford.
The England forward went down under a challenge from goalkeeper Lukasz Fabianski to earn a spot-kick in first half-injury time which was converted by Wayne Rooney, before Gylfi Sigurdsson equalised with a free-kick 11 minutes from time.
Replays showed Rashford engineering contact before going down and Clement was adamant referee Neil Swarbrick made the wrong decision.
"Replays show that the player deceived the referee," he said "There's no other way to look at it.
"You could say he's dangled a leg to get the contact, but he's down before that. He's down before there's any kind of contact.
"The keeper pulled out of it."
There were a number of bodies between Rashford and referee Swarbrick, who delayed for several seconds before pointing to the spot.
But Clement confirmed he had discussed the incident with the official at full-time and was told he had seen it clearly.
"I looked at the reaction of my players first of all and they were furious about it," he added. "That puts a doubt in your mind whether it's the correct decision.
"Also the delay between the contact - or non-contact - and the decision being given. There was a brief pause there that which normally would say there's doubt.
"The referee said to me after the game he was sure what he'd seen and he was just confirming with the assistant. I don't know why I even asked him because he was almost as far away as I was."
Jose Mourinho had little to say on the incident, only adding: "I don't have a view because I didn't watch and I have Marcus' opinion. He said that the goalkeeper touched him."
The opening goal came at the end of a first half which saw Swansea enjoy more possession than the home side and create a number of clear chances.
Clement was proud of their second-half fightback, which leaves them two points adrift of Premier League safety with three games to play.
"I'm very pleased with the players and the performance," he said.
"I think we showed a lot of different qualities today. We can come to a difficult place with all the great support they have here and actually take the ball, play well and create some good chances.
"Then we also dealt with a goal going in against us under difficult circumstances, not feeling sorry for ourselves and getting on with the job.
"When the goal went in, the least we deserved was that."