Clermont's remarkable four-year undefeated home record to 74 matches
Five-time champions Biarritz were relegated from the French Top 14 on Saturday ending an 18-year stay in the elite division.
Biarritz, founded in 1913 and boasting legendary international fullback Serge Blanco as president, had their fate sealed by a 16-10 defeat at Perpignan.
Despite boasting the talents of skipper Imanol Harinordoquy and Dimitri Yachvili, the signs of decline were evident in recent seasons with ninth-place finishes in 2012 and 2013 making the title triumphs of 2002, 2005 and 2006 look distant memories.
On Saturday they were holding on at 10-10 at the interval against Perpignan.
Welsh centre Aled Brew gave them a confidence-boosting edge with an 11th-minute try converted by Julien Peyrelongue, but Perpignan's English winger Richard Haughton scored a try on 20 minutes, converted by Welsh star James Hook.
Hook had already kicked an early penalty with Peyrelongue also knocking over an injury-time three points for 10-10 at the break.
However, Hook succeeded with two second-half penalties to give Perpignan victory and send Biarritz into the second division despite four more matches still to play.
Blanco and Biarritz manager Laurent Rodriguez left the Stade Aime-Giral by a sidedoor with just the 33-year-old Yachvili, the 59-capped scrum-half facing the media.
"We were practically down, now it's definite," said Yachvili, who has been at Biarritz through thick and thin since 2002.
"We have four games left, we will play for the jersey's honour. I am sad and disappointed, but that's life."
Montpellier went third in the standings with a 22-8 win at Oyonnax and are level on 61 points with European champions Toulon who were beaten by new leaders Clermont 22-16 on Friday.
That win extended Clermont's remarkable four-year undefeated home record to 74 matches.
Defending champions Castres are fourth after a 38-6 victory over Brive with Stade Francais and Toulouse making up the top six places.
Toulouse snatched a thrilling last-minute 27-27 draw with Stade when replacement prop Yohan Montes crashed over for an injury-time try under the posts, converted by Jean-Marc Doussain.
Stade looked to have the upper hand, having led 27-8 at half-time, but Toulouse came storming back in the second period, eventually outscoring their hosts at the Stade de France - in front of a 63,000-strong crowd - by four tries to three.
"Never would I have thought we were capable of getting back into this match," Toulouse coach Guy Noves acknowledged.
Noves' Stade Francais counterpart Gonzalo Quesada was left equally stumped by the result.
"I'm trying to understand," the Argentinian sighed. "We never said 'our work's done', we knew Toulouse would come back out with intent.
"We suffered but with a 19-point advantage, we should have shown better game management."
Toulouse's former All Black playmaker Luke McAlister scored one of his team's tries but staggered off after 13 minutes with a back injury.
Stade's Julien Dupuy opened the scoring with a long-range penalty after McAlister had missed an earlier effort for Toulouse.
The feisty scrumhalf then sliced between McAlister and Patricio Albacete for a gift of a try he also converted.
But Toulouse came firing straight back, centre Gael Fickou pouncing on a loose kick-off and driving forward, McAlister taking Pascal Pape with him as he crossed the line from the resulting ruck.
With Dupuy at the heart of Stade's driving game, the former Leicester player again split the defence and a smart offload saw halfback partner Jules Plisson over for the Paris team's second try.
Dupuy was again on the mark with a penalty to push Stade's lead to 20-5, soon extended by seven points when lock Alexandre Flanquart crossed after a break by ex-Springbok centre Meyer Bosman and a good offload by Pape.
Replacement Doussain pulled back a penalty for Toulouse, who started the second-half with a neatly-taken try by South African scrumhalf Jano Vermaak after a storming break from Fiji flanker Akapusi Qera.
Toulouse replacement Joe Tekori made an instant difference after then taking the pitch, the towering Samoan setting up the drive and penalty from which he crashed over for a converted try that dragged his team back to within seven points.
Stade's Benjamin Macome was sin-binned for a ruck infringement with 15 minutes left, and for all that Toulouse pushed, they could not break through a resolute defence.
Fijian wing Waisea Vuidravuwalu produced a last-gasp, try-saving tackle on Toulouse's New Zealander Hosea Gear, but it was not finished as the pressure finally paid off and Montes bullocked over, Doussain making no mistake with the extras.