Five-time French champions Biarritz's continuing fall from grace saw them relegated Friday to the third division from the ProD2 because of financial problems.
The club, last winners of the French league in 2006, were relegated from the elite Top 14 in 2014, and will from next season play in Federale 1, according to the LNR, the body that runs professional rugby in France.
Biarritz, twice runners-up in the European Cup (2006, 2010) and Challenge Cup winners in 2012, have seven days in which to appeal to the French rugby federation over their relegation.
The LNR's financial watchdog had previously asked the Basque club to stump up one million euros to ensure an adequate budget for the 2018/19 season.
Biarritz's woes saw former France international full-back Nicolas Brusque stripped of the club presidency in February by majority shareholders A-Team Sports Investments (ATSI), which holds a 52% share in the club.
Brusque's successor Benjamin Gufflet, owner of the Surf Session magazine, only lasted 53 days as infighting gripped, and continues to grip, the club, currently presided over by Benoit Raynaud.