Smith was clearly angered by Murphy's offside decision against Kris Boyd before the Rangers striker volleyed the ball into the net in the second half. Referee Steve Conroy's whistle had sounded and everyone – including Motherwell goalkeeper Graeme Smith – had come to a standstill before Boyd scored his 'goal'. The Ibrox manager, however, not only held the linesman culpable, but referred back to another incident in the Old Firm match Celtic won 3-2 at Parkhead last April.

"That was a poor decision by the linesman, as it was clear that Boyd was onside," said Smith. "Mr Murphy was quick to allow a Scott McDonald goal to stand at Parkhead last season and quick to disallow that one tonight. We're a club who supposedly don't get decisions given against us. Well, that's two away from home this season, at Aberdeen and here tonight that have cost us." In the 1-1 draw at Pittodrie, DaMarcus Beasley scored in injury time, but the goal was disallowed for offside.

"Having said that," added Smith, "we had enough chances to win the game, especially in the first half. But we missed them all, so, in that respect, we only have ourselves to blame."

Smith's criticism of Murphy could earn him a summons from the SFA to explain himself. His counterpart, Motherwell manager Mark McGhee, countered the Rangers manager's claim of injustice with one of his own.

"Rangers may think their goal was all right, but we should have had a stonewall penalty at the very end," said McGhee, in allusion to a pull on his striker, John Sutton, in injury time. "Some people thought I was a bit harsh on my players when I said I was disappointed with their performance against Celtic last Saturday. But, whatever anyone thought of the performance, it wasn't good enough to prevent us from losing the match. I think tonight showed what I meant when I said I was disappointed with them.

"Our goalkeeper, Graeme Smith, did play well, but Allan McGregor had to make some top-class saves as well. Graeme became a father yesterday, his wife had a little girl, Mia, and maybe that inspired him. But he's been greatly improved since the start of this season."