Clermont bounced back with a dominant four-try performance, reclaiming the top spot they had briefly relinquished to La Rochelle.
Having suffered a surprise 26-20 loss to Toulouse last weekend, Clermont bounced back with a dominant four-try performance, reclaiming the top spot they had briefly relinquished to La Rochelle on Saturday.
"This is a great start to January with a lot hinging on it for our season," said Clermont centre Remi Lamerat who scored his team's fourth try.
"Not only is it good to have beaten Toulon but it's even better to have taken the offensive bonus point which was not an objective. Now, we will be able to take this form into the European Cup."
Clermont were 8-3 ahead at the interval with Camille Lopez scoring the first half's only try.
They stepped on the gas after the break with a penalty try followed by a score by Wesley Fofana, who intercepted a careless pass by Toulon's Australian full-back James O'Connor, and a late try from Lamerat.
Clermont ended the weekend with a one-point lead over La Rochelle and are five ahead of Montpellier in third. Toulon stay fifth, 10 points off the pace.
Toulon's misery was compounded when veteran French winger Vincent Clerc, starting for only the second time this season after undergoing an Achilles tendon operation, was replaced late on with what looked like a serious left leg injury.
"Toulon were European champions three times but we have to admit now that this period is over," said Toulon coach Mike Ford.
"We have to go back to work and improve certain things."
French international winger Yoann Huget grabbed two late tries to seal Toulouse's 18-15 comeback win at Stade Francais, condemning the Paris side to a first home defeat of the season.
Stade were in control at 15-6 with just 10 minutes left after Jules Plisson, playing instead of injured South African star Morne Steyn, had kicked four penalties and a drop goal for a perfect five-from-five haul.
Toulouse fly-half Samuel Marques had popped over a penalty either side of the interval to keep the visitors, who had stunned leaders Clermont 26-20 last weekend, in touch.
But the match turned after 63 minutes when Stade lock Paul Gabrillagues was yellow-carded for repeated infringements.
Toulouse pounced to cut the deficit to 15-11 thanks to Huget's opening try on 70 minutes which came just moments after they had been unfortunate not to have been awarded a penalty try.
Sebastien Bezy converted for 15-13 before Huget grabbed his second, crucial try almost from the restart after full-back Maxime Medard had caught Stade on the back foot with a smart breakaway.
Bezy missed the conversion but Toulouse clung on for a victory which moved them up to fourth place in the table while Stade are fifth from bottom.
"It's a great win for us," said Toulouse coach Ugo Mola. "In recent games, things didn't go our way. But tonight, it all worked out in our favour."
Stade boss Gonzalo Quesada believes Huget's deciding try should have been ruled out for a forward pass.
"It's tough but we have nothing to reproach the players for. On the contrary, they showed great spirit against a very good Toulouse side."
On Saturday, La Rochelle had snatched top spot with a bruising 22-8 win over an indisciplined Castres who gave up 20 penalties and saw skipper Rodrigo Capo Ortega and Rory Kockott yellow-carded while replacement prop Yohan Montes was red-carded for appearing to aim a head butt at Mohammed Boughanmi after being on the pitch for just five minutes.
All Blacks World Cup-winning flanker Victor Vito scored his first try for La Rochelle.