The Red Devils signed the Belgium international in a £75m deal from Premier League rivals Everton last summer.
Lukaku has scored 12 goals in 25 games in the Premier League in his first campaign at Old Trafford.
The Belgian forward has gone through long goal droughts in the 2017-18 season to prompt criticism of Lukaku.
The Manchester United centre-forward has struggled to retain the ball and bring team-mates into the game.
Former Irish defender Kilbane believes Lukaku is limiting Manchester United’s ability to produce their attacking brand of football.
“So often, as I’ve said before, Lukaku scored his goal but far too often the ball is bouncing off him,” Kilbane told Irish radio station Newstalk.
“Far too often, he is giving the ball away. It is costing Manchester United.”
Lukaku has netted 18 times in 37 games in all competitions in the 2017-18 campaign to make a decent if unspectacular start to life at Old Trafford.
The Manchester United striker will be hoping to fire the Red Devils into the Champions League quarter-finals with a victory over Sevilla later this month.
The 20-time English champions are in the FA Cup fifth round but lost 2-1 to Bristol City in the League Cup semi-finals last month.
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