Mauricio Pochettino has described his team's performance against Monaco in Sunday's Ligue 1 defeat as "a disgrace."
Following Lionel Messi's flu-related absence prior to the trip to the Stade Louis II, the runaway Ligue 1 leaders were shredded 3-0 by Philippe Clement's team.
Wissam Ben Yedder scored twice on either side of Kevin Volland's goal to give Monaco a spectacular victory, and Pochettino has chastised his team for their lack of "fighting spirit."
Speaking to the press after the defeat, Pochettino said: "It's unacceptable to start a game like that. After that, it was a disgrace in sporting terms.
"Now it's time to move on, get over the frustration of the Champions League and think about giving our best while having a competitive attitude. I don't want to look for excuses.
"The first half was unacceptable. We had no fighting spirit. The way we played is not acceptable. This can't happen. We can't have this kind of attitude. It is unacceptable to start the game in this way. Respect for the club and our fans is fundamental. The important thing is to find solutions.
"Behaviour must be more collective than individual. We have moved away from that. We have to think collectively."
PSG's advantage atop the standings has been whittled down to 12 points following Marseille's 2-1 victory against Nice later on Sunday.