PSG's 3-0 win at Reims on Saturday gave them a seven-point lead at the summit, but second-placed Lille trimmed back that advantage as they kept a ninth consecutive league clean sheet at home to Toulouse.
Toulouse were in the ascendency for long periods during the first hour, with Lille goalkeeper Vincent Enyeama to the fore, but the game turned when the visitors' Argentine forward Oscar Trejo collected his second yellow card of the second period for a tackle on Idrissa Gueye in the 57th minute.
Lille finally broke the deadlock five minutes from time when Pape Souare powered home a header from a Florent Balmont cross.
Monaco are a point behind Lille after winning at Nantes by the same scoreline.
The decisive moment arrived in the 70th minute when, following relentless Monaco pressure, Mounir Obbadi's deflected 25-yard strike defied Nantes goalkeeper Remy Riou.
Saint-Etienne moved into sixth, one place behind Nantes, courtesy of another 1-0 scoreline at Nice.
Mevlut Erding poached the only goal in the 20th minute but the game was marred before kick-off when the visiting supporters were ejected from the stadium after tearing out seats and throwing them towards home fans.
