Referee Craig Thomson admits he should have awarded Celtic a second penalty in their Old Firm defeat by Rangers at Ibrox.
With Rangers leading through a Kenny Miller goal, Thomson ignored appeals for a spot-kick in the 12th minute when Shaun Maloney went to ground in the box following a challenge by Gers skipper David Weir.
Thomson did award the Hoops a penalty in the 25th minute after Rangers defender Sasa Papac tripped Parkhead debutant Zheng Zhi and Aiden McGeady scored from the spot. However, by then, Miller had grabbed his second and the Ibrox side held onto their lead to go within a point of Tony Mowbray's side at the top of the Premier League.
In a match which had more than its fair share of contentious issues, Maloney and Celtic defender Mark Wilson were booked for diving but through the Scottish Football Association's Head of Referee Development, Hugh Dallas, Thomson pled guilty to denying Maloney a penalty.
Dallas said: ''Taking charge of an Old Firm game is both high profile and challenging. Referees are well aware that their performance will be judged on calling the major decisions correctly.
''Craig and I have had our post match de-brief. Whilst I would compliment Craig for his overall handling of yesterday's encounter, he is disappointed at his error of judgement when he decided against awarding a penalty to the visiting team in the 12th minute.
''Our referees are fitter than they have ever been and our referees are better prepared for matches than they have ever been. We are working each and every day with our top officials to make sure that they are in a position to get the big calls right. However, mistakes are part and parcel of football.
''I think that it says a lot for the character and professionalism of Craig that he has been more than willing to hold his hands up on this one.''