A late penalty from fullback Scott Spedding made it back-to-back victories for Clermont over Saracens in the Champions Cup.

Ben Spencer's early try helped the European champions into a 13-0 lead but the three-time runners-up chipped away at it thanks to the boot of Morgan Parra.

The scrum-half surpassed 500 European points as he landed five kicks to add to Spedding's long-range penalty to make it 18-13, before Alex Lozowski went over for Sarries' second try to get them back in front.

But, after Parra locked the scores, Spedding kicked Clermont to a 24-21 victory that inflicted a seventh straight defeat on Saracens, who need two wins from their final two matches to give themselves a chance of advancing to the quarterfinals.

Clermont tighthead prop Rabah Slimani failed to roll away at a ruck to give Owen Farrell the opportunity to put his side ahead, and he sent the penalty between the uprights for a 3-0 lead after four minutes.

He kicked another penalty to double the advantage, before Saracens' perfect start got even better.

Scrum-half Spencer picked the ball up and sold Slimani completely with a dummy from the base to slice through the defence.

He stepped off his left foot and managed to ride the tackle of David Strettle to score, and Farrell converted to take his side 13 points clear after 10 minutes.

Parra narrowed the gap to seven points with a pair of penalties of his own, before last week's Saracens tormentor Alivereti Raka limped off injured after a breathless period of play.

But Clermont received a boost when Will Skelton was yellow carded for a high tackle, allowing Parra to make it 13-9.

Marcelo Bosch missed the chance to take Sarries a converted try clear, but Spedding made no mistake on the stoke of half-time to ensure Clermont only had a one-point deficit to overturn in the second period.

And the hosts were ahead seven minutes into the second half when Parra surpassed the 500-point mark in European competition after Farrell strayed offside.

Parra made it six penalties from seven attempts after a heavy forward drive to move Clermont into a 18-13 lead.

Farrell maintained his 100 per cent record to cut the deficit to two points before Nick Abendanon was shown yellow for taking a man out in the air at the restart.

The defending champions made Clermont pay when Sean Maitland's mazy run piled on the pressure deep in the home 22, before the ball was worked wide again for Lozowski to touch down.

But Juan Figallo failed to roll away at a ruck to earn a yellow card and allow Parra to level the scores.

And with the match on the line, Clermont earned a scrum penalty, which Spedding smacked over from long range.