Lille's European hopes were dented as they were held to a surprise 0-0 draw by Nantes, allowing Lens to move second.
Claude Puel's Lille began the day 13 points adrift of leaders Lyon and failed to make considerable inroads as they were frustrated by their resilient opponents.
Eric Carriere (29) and Seydou Keita (45) found the target for Lens in the first half at Valenciennes, and Issam Jomaa (pictured) finished off a 3-1 victory in stoppage time after Steve Savidan scored from the penalty spot (61) for the home side.
Sedan hit back from Bafetimbi Gomis' early goal (10) to stun high-flying St Etienne 2-1, with former Middlesbrough man Joseph-Desire Job (46) pulling them level and a Lamine Diatta own goal (72) sealing victory.
Sedan remain bottom though, as Nice also claimed a surprise 2-1 victory over Bordeaux. Honorato Ederson bagged a brace for Nice (12 and 26), before Johan Micoud netted for Les Girondins.
Frederic Piquionne scored a penalty on debut as Monaco defeated Auxerre 2-1. Serge Gakpe broke the deadlock for Monaco after 36 minutes and Piquionne struck after 62, before Kanga Akale grabbed a last-gasp consolation for Auxerre.
Nancy beat Toulouse 2-1 thanks to goals from Gaston Curbelo (14) and Marc-Antoine Fortune (76). Bryan Bergougnoux scored for Toulouse in the 90th minute.
Steve Marlet sealed a last-minute 2-1 victory for Lorient against Le Mans, after Yannick Fischer's own goal (53) had cancelled out Grafite's opener on the stroke of half-time.
The evening's final game, between Sochaux and Rennes, finished goalless.
Click below for individual match summaries:
Lille 0-0 Nantes
Lorient 2-1 Le Mans
Monaco 2-1 Auxerre
Nancy 2-1 Toulouse
Nice 2-1 Bordeaux
Sochaux 0-0 Rennes
St Etienne 1-2 Sedan
Valenciennes 1-3 Lens