Saracens racked up a half-century of points against Northampton Saints for the fourth time this season with a 63-13 rout in the Premiership.

Bottom side London Irish caused an upset, consigning Harlequins to a heavy home defeat on Sunday (AEST).

Sarries hammered Saints in the first game of the season and consigned it to two European Champions Cup thrashings before running riot again in a nine-try demolition job at Franklin's Gardens.

Mark McCall's men reign as European champions was ended by Leinster last weekend and Saints felt the backlash, conceding seven second-half tries in a mauling.

There were only two points in it at half-time, Alex Lozowski rounding off a fluent move to score the opening try and Schalk Brits powering his way over after Reece Marshall peeled off the back of a maul to dot down for Saints.

Saracens blew sorry Saints away in the second half, Ben Spencer and Mako Vunipola crossing to snaffle the bonus point and Liam Williams getting on the end of a clever Owen Farrell kick to add another five-pointer.

There was no let-up from the London side, Chris Wyles, Sean Maitland, Jackson Wray and Nathan Earle also going over and Farrell scoring 18 points from the tee as they reduced Exeter Chiefs' lead at the top to just three points.

London Irish look to be heading back to the Championship, but did the double over Quins with a 35-5 bonus-point victory.

The Exiles beat John Kingston's men on the opening day of the season and claimed only their third Premiership win of the campaign at the Stoop, Piet van Zyl scoring twice as they led 22-0 at the break and Max Northcote-Green and Tom Fowlie also crossing the whitewash.

Second-bottom Worcester Warriors are nine points better off than London Irish after striking a blow to Newcastle Falcons' play-off hopes with a 27-13 win with a brace of tries for David Denton.

Leicester Tigers are up to third after knocking Newcastle out of the top four with a 34-19 victory over Bath at Twickenham which stretched their winning run to five matches.