Toulon romped to a bonus point victory at home to Biarritz on Saturday to consolidate their hold on the Top 14 leadership.
For the second time in three home games they crossed the 50-point barrier as they raced in six tries in a 50-15 success against the Basques.
However, Clermont held the leaders' gap at two points as they also managed an attacking bonus in their 37-10 defeat of fourth-placed Castres.
Tries from Rudolffe Wulf and Sebastien Bruno in the final seven minutes ensured Toulon took the offensive bonus point to maintain their gap on Clermont.
In an entertaining first period South African lock Bakkies Botha and Australian centre Matt Giteau got on the scoresheet.
Alexis Palisson scored a try and a drop goal while English lock Nick Kennedy also got on the scoresheet as compatriot Jonny Wilkinson finished with a personal haul of 17 points.
Fiji's Napolioni Nalaga scored a converted try three minutes from time to ensure Clermont took their bonus point after winger Romain Martial looked to have denied them just a couple of minutes earlier with Castres's only try of the game.
In France a team must score three more tries than their opponents in order to secure the bonus point.
Earlier scores from Fijian Sitiveni Sivivatu and South African Gerhard Vosloo, as well as a penalty try, had seen Clermont, for whom Australian Brock James kicked 17 points, cruising to victory.
The results added further weight to the feeling that this season's title race, as well as the European Cup, will likely boil down to a straight shoot-out between the top two in the Top 14.
It was much harder going for reigning champions Toulouse who, shorn of a host of international stars, limped to a 33-32 win over lowly Bordeaux-Begles.
Toulouse were even outscored four tries to two and had a Lionel Beauxis penalty 12 minutes from time to thank for their success.
Beauxis landed six penalties and a conversion while New Zealander Luke McAlister added another penalty. Veteran hooker William Servat and winger Yves Donguy touched down for the hosts.
Australian Blair Connor, South Africa's Heini Adams, hooker Laurent Delboulbes and Matthew Clarkin of New Zealand went over for the visitors, who remain third from bottom but did at least garner a losing bonus.
Perpignan held off a late Grenoble rally to squeeze out a 20-18 victory and draw level on points with Montpellier in the race for the sixth and final play-off spot.
On Friday night Racing Metro recorded an eighth straight victory with a crucial 17-15 success at Montpellier that took them level on points with Castres.