Lukaku turned a Kevin de Bruyne cross towards his own goal and David Silva pounced to score City’s opener before half-time.
He then made a hash of clearing a cross from Silva in the second-half, with his punt clear from inside the area smashing into the back of team-mate Chris Smalling and landing at the feet of Nicolas Otamendi, who fired City back in front after Marcus Rashford earlier pulled a goal back for the hosts.
Man Utd‘s fans were not happy with the Belgian bruiser after his error-strewn display.
“Romelu Lukaku single handily ending our title hopes and giving it to City. sell him” one fan wrote on Twitter.
“Romelu Lukaku has 2 assist for Man City today” added another.
A third posted: “Man United working hard to win this game. Romelu Lukaku working harder to lose it. What a joke!”
United didn’t impress in the opening stages of the game and didn’t get much better after the break.
BBC pundit Robbie Savage said: “You wouldn’t think that City are playing one of the top sides on this showing.
Sky Sports man Gary Neville wasn’t impressed with Lukaku.
“You look at him today and he struggled,” he said. “I’m not just talking about struggling in terms of missing a chance, he struggled at being in the game and being confident in the game.
“He’s got to get over that quickly as he’s Manchester United centre forward.
“He’s a young lad but he needs to get to the point where he believes he should be out there – it’s like he doesn’t believe it in this period.”