Guinness Premiership champions Wasps lurched to their third consecutive defeat of the season as Bruce Reihana bagged 17 points in front of an ecstatic Franklin's Gardens.

The Saints benefited from some Josh Lewsey fumbles in the first half as the England man gifted both opposite number Reihana and winger Chris Ashton with easy tries.

Wasps though also benefited from Reihana's wayward kicking as the full-back missed three penalties to leave the match perfectly poised at 14-14 heading into the second half.

The match remained on a knife edge until wing Sean Lamont went over 12 minutes from time to leave several unanswered questions at Wasps director of rugby Ian McGeechan's door.

Despite the contribution of Reihana, the game was won in the pack where the outstanding Ignacio Fernandez Lobbe outmuscled the Wasps forwards.

In front of a sell-out crowd, the hosts made the perfect start in the opening minute when Lewsey's clearing kick was charged down by Reihana, who gleefully gathered up the loose ball to touch down before converting.

Dave Walder pulled three points back for Wasps on eight minutes, kicking a penalty from just outside the Saints 22 after they were penalised for not releasing.

Two minutes later, Wasps went in front when a quick passing move from a line-out on the far side ended with Dominic Waldouck going over in the corner for an unconverted try.

Saints flanker Scott Gray was then caught offside by referee Chris White on 20 minutes, resulting in Walder kicking three points from 40m before Reihana missed a penalty from the touchline.

But Northampton retook the lead when Lewsey dropped Carlos Spencer's kick, and Chris Ashton, who grabbed 39 tries in National One, ran in under the posts for his first score in the Premiership.

On 32 minutes former All Black Reihana hit the upright from a penalty from 45m, before missing one from a similar distance two minutes later.

And Walder showed him how to do it with a textbook strike right on the stroke of half time.

Northampton moved three points ahead just after the restart when Reihana kicked a close-range penalty only for Walder to immediately haul them level.

Both sides reduced to 14 men on 48 minutes when Rob Webber and Dylan Hartley were sent to the sin bin for using their knees on each other in the tackle.

In an electric atmosphere, both Reihana and Walder missed a penalty apiece before the Wasps fly-half landed a penalty kick from just inside his own half to make 20-17.

But on 68 minutes replacement Stephen Myler's long, cut out pass to the left wing found Lamont who went over with Myler converting from out wide.