Les Dogues looked to have sewn up the three points which looked like it would see them into third place in Ligue 1, but Cedric Kante's goal and a brace by Vincent Nogueira ensured that Les Lionceaux left the Grand Stade Lille Metropole with a share of the spoils.
"It is professional misconduct," Garcia told reporters. "You can not lead 3-0 in the 70th minute at home against a relegation team and be held in check in the end.
"From the moment we stopped playing we were punished. We thought at 3-0 it was finished, we did not need to provide the effort. The problem is that when you do not play, you become an average team.
"I am devastated and angry. I'll try to keep what I have in my heart for the debriefing tomorrow morning. We will review the images to analyse how far we were at fault."
Lille are fifth in the table.