Hearts boss Derek McInnes said the decision to award Celtic a 99th-minute penalty was "disgusting" as the Scottish Premiership title race took yet another dramatic twist.
Kelechi Iheanacho tucked away the winning goal from 12 yards, with the decision given after referee John Beaton was sent to the pitchside monitor for a VAR review.
Sam Nicholson was adjudged to have handled the ball despite replays appearing to show he made contact with his head, as Celtic snatched a seismic victory at the death.
It means Martin O'Neill's side head into their final day fixture against leaders Hearts on Saturday a point behind and knowing any victory will see them crowned champions.
Had the game at Motherwell ended in a draw, Hearts would have gone into the final weekend three points clear at the top as they look to land their first title for 66 years.
McInnes was already incensed that Hearts were denied two penalties in a 1-1 draw with Motherwell, and he struggled to contain his anger despite his side's 3-0 win over Falkirk.
"I shouldn't be commenting on another game, but I knew I was going to get asked the question," said McInnes.
"Having seen it, it feels like us against everybody. When you see the two we didn't get at the weekend, and then you see that. How they can arrive at that situation?
"Celtic are more than a touch fortunate to get that penalty. I'm getting more and more dismayed at some of the decisions our referees are coming up with.
"It's such a bad decision. Motherwell must feel totally aggrieved. I had to keep looking at it because I thought I was missing something.
"When I was watching it I had to ask 'what I am looking for here?' It's disgusting."
The Opta supercomputer has predicted Celtic to finish top of the pile, handing O'Neill's side a 50.9% chance of winning the title compared to Hearts' 49.1% probability.
At one point on Wednesday, with Motherwell ahead in the 17th minute through Elliot Watt, Hearts were on course to be crowned champions with one game to spare.
Hearts are looking to win their first Scottish title since 1960 and become the first team other than Glasgow heavyweights Celtic and Rangers to lift the trophy since 1985.
And though McInnes was still visibly frustrated by the events that unfolded, he said there is no better place for a game of this magnitude than Celtic Park.
"We've got that final showdown game so it's perfect for Scottish football," said McInnes.
"The drama, the excitement, the spotlight on that, it couldn't be billed any better. We're looking forward to it. We can't wait for the game."