Monaco slipped to third in the table despite coming back from two goals down to draw 2-2 with Ajaccio at the Stade Louis II.
Ajaccio raced into an early lead after eight minutes when a quick free-kick caught the hosts by surprise and Khalid Boutaib was on hand to nod Issiaga Sylla's delivery beyond Danijel Subasic.
As Monaco continued to disappoint, the visitors' evening improved further when Mohamed Larbi was allowed space on the right before pulling the ball back to John Tshibumbu to add a second just after the half-hour mark.
The principality side were given a perfect opportunity to get themselves back in the contest when, just five minutes after the restart, goalscorer Tshibumbu turned villain with a foul on Fabinho inside the area.
The Brazilian full-back took charge of the resulting spot-kick and reduced Ajaccio's advantage with a well-taken penalty which just beat the outstretched Clement Maury.
With the wind in their sails, Monaco pressed for a leveller and almost found it when Guido Carrillo's close-range header beat Maury only to be denied by the crossbar.
And, after Bernardo Silva failed to capitalise from Joao Moutinho's cutback, Monaco finally got reward for their improved second-half performance.
Ajaccio keeper Maury was at fault after he failed to claim Moutinho's corner and Ricardo Carvalho was left with a simple finish on 73 minutes to level the score.
The visitors went closest to taking maximum points twice in injury time but Boutaib's effort from Alexandre Coeff's delivery failed to find the target before Larbi fired over just before the full-time whistle.