La Rochelle took another step towards the Top 14 semi-finals by defeating Bordeaux-Begles 16-5 on Sunday (AEST), while Bayonne's relegation from the top flight was confirmed.

Surprise leader La Rochelle made it 10 league wins on the bounce and 11 without defeat thanks to Brock James's kicking, the Australian kicking three second-half penalties after converting Kini Murimurivalu's try in the opening period.

The team from the Bay of Biscay holds a comfortable 18-point advantage over third-placed Montpellier, which thumped relegation-threatened Grenoble 54-14 at Altrad Stadium.

Each of Montpellier's eight tries came from a different scorer, with the bonus point accrued moving it to within just four points of Clermont Auvergne in the second semi-final spot.

Clermont succumbed to a shock 26-21 defeat to lowly Brive at Stade Marcel-Michelin, the visitors taking control early in the second half through Matthieu Ugalde and Benjamin Lapeyre despite being a man light from Thomas Laranjeira's sin-binning.

Bayonne failed to show the same resilience as its stay in the top flight was brought to an end by Stade Francais at Stade Jean Dauger.

Hugo Bonneval's try on the stroke of half-time sent Stade into the interval 10-3 up, and it never looked like surrendering a lead that ended in a 32-16 bonus-point win.

Elsewhere, Lyon secured its first Top 14 win away from home this season by edging out Castres 17-16 at Stade Pierre Antoine.