Celtic manager Neil Lennon was facing disciplinary action by the Scottish Football Association after being sent off at half-time in his team\'s Scottish Premier League defeat by Rangers on Sunday. Celtic, in a match where they could have wrapped up the title, lost 3-2 in a fiery Glasgow derby clash at the Ibrox home of arch-rivals Rangers. After complaining to referee Calum Murray about his performance in the tunnel, Lennon was ordered to the stands. Lennon has until Tuesday, April 3, to respond to the SFA\'s \"notice of complaint\". Speaking after Sunday\'s match, he said: \"My sending-off is a joke. I don\'t think I deserved to be sent off. My staff are very angry about it, my players are angry and disappointed. \"I spoke quite quietly and coldly to the referee in the tunnel. I didn\'t swear and didn\'t point any fingers. \"I told him I wasn\'t happy with his first-half performance. I was speaking to the match delegate after the game and their version of events are different from mine but I\'ve got witnesses to back me up. \"Alan Thompson (coach) and our PR person was there, a couple of other members of staff and players.\" A principal hearing date has been set for Thursday, April 19. Earlier on Monday, it emerged Lennon had watched the second half from the Ibrox press room on the advice of Celtic security staff who were concerned for his safety had he taken a seat in the stands. After the match, Lennon said: \"I can\'t sit in the stand for my own safety, that sums things up in this country. \"I would have sat in the directors\' box but I was told for my own safety that it wasn\'t a good idea. I watched the second half in here (the press room).\" Meanwhile a Celtic spokesman said Monday: \"Neil was advised by Celtic\'s own security and operations staff not to enter the stand or directors box area at Ibrox at yesterday\'s (Sunday\'s) match. \"He was then provided another area by Rangers in which to watch the match\". Celtic saw two players -- Cha Du Ri and Victor Wanyama -- also shown a red card either side of Lennon\'s sending-off. And the club announced Monday they would be appealing South Korean defender Cha\'s red card but not that of Kenya international Wanyama. Cha was sent off after 29 minutes for denying Lee Wallace a goalscoring opportunity on the edge of the box. Wanyama then saw red after 57 minutes for what appeared to be a two-footed challenge on Steven Whittaker. \"Celtic are to appeal against the red card issued to Cha Du-Ri during Sunday\'s derby match against Rangers at Ibrox,\" said a club statement. \"There will be no appeal against the red card issued to Victor Wanyama in the second half of the match.\" Celtic pulled two goals back late on in a match Rangers finished with 10 men after Carlos Bocanegra was dismissed for bringing down Georgios Samaras. However, Celtic are still a huge 18 points clear at the top of the table after defending champions Rangers\' 10-point penalty for entering administration gave their Old Firm rivals a huge boost in the title race.