Neil Lennon, the Celtic manager, has vowed to vigorously defend himself after being asked by the SFA to explain his outspoken criticism of referee Willie Collum.

Lennon was furious that Collum did not give a penalty and instead booked Anthony Stokes for diving in stoppage time of Sunday's Scottish Communities League Cup final defeat by Kilmarnock. Stokes went to ground when he was challenged by Michael Nelson, whose tackled appeared to clip his leg.

The Celtic manager spoke with SFA compliance officer Vincent Lunny on Thursday but yesterday morning there was confirmation that Lunny had decided there was a case to answer. Lennon has until next Friday to respond and he will not back down. After he responds, Lunny can either offer a fixed suspension, take no action, or let the matter pass into the hands of an SFA judicial panel for a decision.

Lennon had said Collum's decision was "absolutely shocking", "criminal", "awful refereeing" and "has cost us the treble".

But he was unrepentant when reacting to news of the SFA's action yesterday. "I spoke to Vincent Lunny on the phone yesterday when the letter came through. I will submit my response by March the 30th and I will defend my case vigorously. I don't even think I need to be up there [the SFA offices] but Vincent and the SFA see it a different way. I'll be quite happy to go and defend my case.

"There are one or two quotes that they felt might be against the rules, whatever rule it is. I don't know. So I asked him if he had looked at the whole interview and he said he had. There are mitigating circumstances within the context of the interview. But people only want to talk about my criticism of the decision rather than look at the whole context of the interview.

"I still maintain it was a penalty kick. I've seen photographic evidence to prove that. I didn't need to, because I saw it about four times from different angles before I was interviewed after the game. I'm convinced it was a penalty.

"Anthony has been accused of being a diver this week, which I can't really tolerate. This team has got the best disciplinary record in the league. One thing we are not is cheats. We are pretty honest. We play the game the right way." Tomorrow's Old Firm match at Ibrox will be refereed by Calum Murray.