Lille won 2-1 at St Etienne on Tuesday to put champions Marseille under pressure and fast-sinking Brest came storming out of the traps to worry Didier Deschamps' side even more.
Striker Loic Remy soon settled their nerves, however, when he netted on 12 minutes after Benoit Cheyrou's ball.
Cheyrou again was the provider with a delicious pass as Jordan Ayew made it 2-0 just before the hour.
Defender Gabriel Heinze added the gloss with an 81st-minute free-kick as Marseille eased to victory at the Stade Velodrome despite forwards Mathieu Valbuena and Andre-Pierre Gignac starting on the bench.
Ten-man Lyon, in third, were humbled 4-0 at mid-table Auxerre and must now battle to stay in the Champions League qualifying spots having slipped 10 points behind Lille.
The future of Lyon boss Claude Puel is uncertain following previous statements by the coach and president Jean-Michel Aulas but Aulas was putting a positive spin on the Auxerre defeat.
"There are still three matches, I hope that we will be able to get some of our injured players back," Aulas told reporters.
"We are going to fight to stay where we are. Third is not shameful."
Puel's side beat Marseille 3-2 at the weekend but their trip to Auxerre started to go wrong when Dennis Oliech netted a 20th-minute opener and defender Dejan Lovren was dismissed for a second booking before half-time.
Alain Traore bagged two goals to further ease Auxerre's outside fears of the drop before Cedric Hengbart completed the rout.
Fourth-bottom Monaco remained in trouble after a 3-0 defeat at Sochaux while mid-table Girondins Bordeaux lost their first game since the resignation of coach Jean Tigana, going down 1-0 at Racing Lens to give the second-bottom team a lifeline.
