Marseille maintains pressure on PSG
A superb first-half Benoit Cheyrou free-kick was enough for the hosts to claim all three points which moved them to within six points of Paris St Germain.
In contrast, Corentin Martins' Brest remain rooted in the bottom three after suffering a sixth successive league defeat having failed to score in all but one of those games.
In a game lacking both in quality and goalmouth action, the visitors defended stoutly throughout the first half but found themselves undone by a set-piece just before the break.
Brest midfielder Ousmane Coulibaly hauled down Cheyrou just outside the area and the former Auxerre man curled a wonderful free-kick off the inside of the left post to give the hosts a lead going into the break.
The visitors finally managed to test Steve Mandanda in the Marseille goal in the 50th minute but Christian Benchop's 25-yard drive brought a comfortable save out of the French international goalkeeper.
That failed to bring the visitors to life though and Mathieu Valbuena went close to doubling Marseille's lead but, after darting into the area, his effort flirted with the wrong side of Alexis Thebaux's left post.
The hosts did have the ball in the back of the net again with 20 minutes to play but Lucas Mendes' header from a Valbuena free-kick was rightly ruled out for offside.
Florian Raspentino and Kamel Chafni both wasted good chances to level the score late in the game but the visitors failed to make the breakthrough and Marseille took maximum points.
''We have improved in our weak moments,'' Marseille coach Elie Baup said. ''At the start of the season, we had less control in those weak moments. Now, we stay calm. We manage to keep the ball a bit better when we feel that we can't trouble our opponent.''
Brest stretched its losing streak to six games to remain in the relegation zone.
''We must keep on fighting until the end of the season,'' Brest coach Corentin Martins said. ''As long as we have a chance mathematically to escape relegation, we will hang tough.''
The Associated Press was used in this report.