Celtic's charge towards the Scottish Premier League title was interrupted by a resilient Motherwell side and a debatable refereeing decision at Fir Park tonight. In the end, Martin O'Neill's men were able to extend their lead by a single point following an entertaining six-goal thriller. But they can legitimately claim that they should have had all three points after Johan Mjallby's shot was shown by television replays to have crossed the line, yet was not given as a goal by referee Hugh Dallas.

Who says all the bad luck is currently residing in the blue half of Glasgow? The early stages suggested the match would reflect the two teams' respective league positions as Celtic poured forward. An ankle injury prevented Chris Sutton from taking part but his absence hardly looked like being significant as the chances began to mount for the visitors.

Alan Thompson should have put his side ahead in the sixth minute but failed to finish a move he had started himself with a neat little shimmy turn in the centre of the park that fooled Ged Brannan completely. It allowed him to send Henrik Larsson's new strike partner Didier Agathe in on goal and although goalkeeper Stephen Woods blocked his stabbed effort the ball rolled to Thompson in an inviting position. But Thompson mis-kicked and all the visitors gained from the move was a corner as it deflected away harmlessly off a defender.

Larsson came close soon after with a header from a free-kick and Stilian Petrov suffered a similar fate to Thompson when his well-struck effort deflected wide. But Woods exhibited his vulnerability once more by failing to collect a 14th-minute corner which Larsson immediately headed back into a crowded area where Johan Mjallby was waiting to blast in from unmissable range.

Yet Motherwell immediately showed their mettle by forcing an equaliser within 10 minutes. Derek Adams had already hinted he might be a significant performer for his side in the opening minutes with a couple of charges into dangerous positions and so it proved when the Celtic backline faltered down their right flank.

Joos Valgaeren half cut out a through-ball, allowing John Spencer to put in a cross that Tom Boyd could only help up into the air and when it came down Adams beat Valgaeren and headed into the net.

Motherwell could have taken the lead before the break when John Spencer's piledriver was parried by Jonathan Gould and Adams was first to the loose ball. But on this occasion he was nowhere near locating the net.

It took Motherwell eight minutes after the restart to take the lead for the only time in the game. Brannan was the architect with a superb pass that sent Stuart Elliott heading menacingly for goal and, although he ended up with only a corner, it was enough to supply Lee McCulloch for a headed finish.

McCulloch had been working hard all night but this was his first sniff of goal, although Celtic's marking from the set-piece had certainly let them down. But that lead lasted just four minutes as Motherwell themselves failed to deal with a set-piece, a corner delivered by Thompson. Larsson nodded it down and there was Valgaeren to smash it in from close range.

Then came the frustration of Mjallby's disallowed goal, with replays showing it should have been allowed. As if aggrieved, Celtic were the dominant force and took the lead in the 72nd minute through Jackie McNamara, who simply rolled the ball past Woods after Larsson had set him up.

Yet Motherwell were not to be denied and Mjallby's evening of mixed fortunes took another turn for the worse when he pushed substitute Don Goodman over and Brannan made no mistake from the spot to win a precious point for his side.