Didier Deschamps' team instead could only move three points behind Lille, who surprisingly lost 1-0 at Monaco on Saturday, and have Olympique Lyon on their tail with just eight games left after the third-placed side beat Racing Lens 3-0.
"Given how the match panned out, a point isn't so bad," Marseille coach Deschamps told reporters.
"But at home, it doesn't matter who you face, when you don't impose yourselves you always lose points. It will be a tough battle right to the end. We are still there, all the teams still have difficult matches ahead of them."
Forward Loic Remy put Marseille in front on the half hour when he fired in a rebound after his header was saved.
The champions had other chances before Norwegian midfielder Daniel Braaten levelled for Toulouse deep into first-half stoppage time with an angled left-foot shot after a static Marseille defence gave him space.
Despite the setback, the Stade Velodrome assumed their side would rise again in the second period despite the unseasonable heat but instead it was the visitors who continued to press.
FOUND WANTING
Argentine defender Mauro Cetto headed in a free kick just after the hour mark with the home defence again found wanting.
Deschamps immediately threw on striker Gignac, who had expected to start, in a bid to conjure an equaliser and the noisy crowd tried to rouse their troops.
Impatient groans soon filled the steamy south coast air as a penalty appeal and opportunities to equalise went begging before Gignac finally netted from Remy's cross six minutes from time.
The France striker refused to celebrate the goal given his Toulouse connections.
Lyon, who conceded twice in stoppage-time last weekend to draw 2-2 with Nice, are again just two points behind their rivals after a home win over a second-bottom Racing Lens side that now lie seven points from safety.
Claude Puel, whose future as Lyon coach beyond May has again been put in doubt by the club presIdent, had to wait until the 55th minute for a breakthrough and even then it was an own goal by Henri Bedimo.
Jimmy Briand made the game safe five minutes later when he headed in a corner and Lisandro Lopez scored a third in injury-time to send Lyon within five points of leaders Lille and above Stade Rennes, beaten 2-0 at Stade Brest on Saturday.
Montpellier in sixth drew 1-1 with struggling Nice.
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