A faultless kicking display by Jonny Wilkinson provided the backbone to Toulon's sixth win in six Top 14 matches on Saturday as they ran out 33-12 winners over high-flying Castres.
Wilkinson kicked 18 points while his team scored three tries which was enough for a bonus point.
That took them four points clear of 2010 champions Clermont, who beat Grenoble 44-20, while defending champions Toulouse, who thrashed Bayonne 35-6 on Friday, are seven points off the lead.
While fiery Toulon owner Mourad Boudjellal vented his spleen at a section of the Toulon supporters for booing a singer he had hired for the day, Toulon coach Bernard Laporte revealed the victory came at a cost to the club.
"We won't get ahead of ourselves even if we are happy to have 27 points after six games," said the former France coach, who is bidding to guide the club to only their fourth title and first since 1992.
"There was a deal struck that the players would get a week of holidays if they won these six games. When I agreed the deal with the players I didn't imagine it would come about.
"Those with whom the deal was agreed won't train this week and therefore will not play against Toulouse. However, we will not select a joke team because we respect those who we play against."
Toulon wasted little time in taking the match by the scruff of the neck as Wilkinson first punished a Castres infringement with a penalty and then converted former Wallaby star Matt Giteau's try, after the latter had intercepted a Castres pass and touched down.
The visitors got themselves off the mark shortly before the 20 minute mark through a superb long range penalty by South African scrumhalf Rory Kockott after France centre Maxime Mermoz went offside.
They reduced the gap further soon after when Toulon's English fullback Delon Armitage was penalised for a high tackle and Kockott made no mistake while the referee gave the Toulon a players a dressing down about their high penalty count.
However, the hosts answered in the best fashion possible as scrumhalf Frederic Michalak slipped a pass to hooker Jean-Charles Orioli 22 metres out and he broke three tackles to touch down - Wilkinson added the conversion for 17-6.
Castres, though, wouldn't give up and two more penalties by Kockott kept them in touch, but Wilkinson made it 20-12 early in the second-half as he dropped a goal in front of the posts after being set up by Michalak and stretched the lead further in the 53rd minute with a penalty.
Five minutes later the Englishman added another penalty to leave Castres requiring two converted tries to get their noses in front.
However, it was Toulon who got a try as Wilkinson fed Mermoz who passed to former Wallaby George Smith and he broke through the Castres centres to touch down under the posts - Wilkinson converted to send the home supporters into rapturous celebrations.