LONDON (Reuters) -- The Scottish Football Association has condemned the violent scenes at Wednesday's Old Firm derby between Celtic and Rangers where coaches Neil Lennon and Ally McCoist had to be separated after an acrimonious confrontation.

"The unedifying sight of two of the country's most recognisable and respected coaches engaged in an angry confrontation was not only unsavoury but exacerbated an already incendiary atmosphere inside the stadium and throughout the West of Scotland," said Scottish FA chief executive Stewart Regan on Thursday.

"The Scottish FA categorically condemns the inflammatory and irresponsible behaviour throughout last night's Scottish Cup replay between Celtic and Rangers at Celtic Park."

Mark Wilson scored the only goal of a fiery encounter in which Celtic overcame nine-man Rangers 1-0 to reach the Scottish Cup quarter-finals, Steven Whittaker was sent off after 34 minutes and El-Hadji Diouf was dismissed after the final whistle.

"I was both saddened and deeply embarrassed to witness the scenes that unfolded during what is supposed to be Scottish football's flagship fixture: these images were broadcast around the world and shows our game in a poor light," added Regan.

The Scottish FA said an investigation into the ugly scenes where 34 arrests were made inside the stadium has already been launched, though Regan added a lot of work would be needed to address the problem.

"A degree of faith in Scottish football was lost last night. All parties must work together to help restore it," he said.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.