Stade Francais opened up a 15-point lead in the French championship on Saturday with their ninth win in nine games but fellow powerhouses Biarritz, the reigning champions, and Toulouse crashed to defeat.
Stade saw off Albi 25-12 in a match played in difficult conditions following a torrential downpour midway through the first half in the French capital.
Biarritz, meanwhile, suffered their fourth defeat of the season after a 20-18 loss at Agen while Toulouse conceded five tries in a 46-9 mauling at Clermont.
Center Thibault Lacroix scored Stade's only try in the 16th minute with the team's other points all coming from the boot of David Skrela. South African Andre Hough kicked all of promoted Albi's points.
Clermont maintained their 100-percent record at home with a fifth win as they moved into second place with their destruction of former European champions Toulouse.
They were always in charge racing to a 19-0 lead at the interval with lock Loic Jacquet scoring after a poor clearance from Yannick Jauzion fell invitingly for the forward to score in the 35th minute.
Brock James kicked three first-half penalties. Clermont skipper Aurelien Rougerie went over two minutes into the second half before flanker Elvis Vermeulen and centers Gonzalo Canale and Pierre-Emmanuel Garcia completed the rout.
Jean-Baptiste Elissalde scored three second-half penalties for Toulouse. Defending champions Biarritz saw their season plummet to a new low when they lost 20-18 at Agen to crash to their fourth league defeat of the campaign.
The loss came hot on the heels of their midweek defeat to Montauban and means they will lose more ground on top two Stade Francais and Toulouse.
At half-time they led 12-10, extended it to 18-10 and looked on course to register their first win at Agen since 1997 with all their points coming from the boot of Dimitri Yachvili. But Agen stormed back.
A Francois Gelez penalty cut the deficit before center Luc Lafforgue grabbed his team's second try on the hour to level the contest. Gelez kept his cool to convert the try and secure victory for his side. Matthieu Lievremont had also crossed for a sixth-minute try for Agen.