Celtic manager Brendan Rodgers says Motherwell violated the spirit of football after the visitors scored a contentious goal at Parkhead in the Scottish Premiership on Sunday.
Celtic were 2-0 up early in the second half when they put the ball out of play to allow treatment to their midfielder Ryan Christie.
Instead of letting Celtic regain possession from the resulting throw-in, Motherwell's James Scott hared after the ball and forced a save from goalkeeper Scott Bain, with Gboly Ariyibi slotting home the rebound to make it 2-1.
The goal sparked a melee and brought an element of needle into the game, which Celtic went on to win 4-1.
"It's a goal that goes against the ethics of the game, and that's the disappointing aspect," Rodgers said.
He suggested that the visitors should then have let Celtic score an uncontested goal to atone for Scott's actions.
"Motherwell had an opportunity then to do something in the spirit of the game, but chose not to and went on to press for an equaliser," he added. "It was a real injustice."
Motherwell boss Stephen Robinson said 18-year-old Scott had made a "mistake" and got carried away by the occasion but added that the reaction had been over the top.
"He's a young boy, he's living his dream by playing football. He’s on flipping £200 a week," he said.
"Celtic didn't lose the league because of it, they didn't lose the game."