Saints' woes deepened as they suffered a last-gasp 24-22 defeat to Newcastle Falcons on a freezing Friday night at Franklin's Gardens.
Nili Latu's try and Sonatane Takulua's conversion snatched the victory for the Falcons after the clock had hit 80.
Saints had looked set to secure a much-needed win after Dylan Hartley's try and five points from Piers Francis added to Harry Mallinder's effort and a penalty try.
But Newcastle, who had gone 14-5 up during the first period through scores from Sinoti Sinoti and Josh Matavesi, kept battling and Latu powered over late on.
It brought a feeling of utter deflation to the Gardens and there were a few boos at full-time as Saints suffered their fifth successive Aviva Premiership defeat.
Jim Mallinder's men have now lost eight of their past nine matches in all competitions and the pressure is mounting.
Saints had headed into the game desperate for a victory and they looked to have got off to the perfect start.
The TMO was called into action just nine seconds in after Rob Horne dived over the whitewash.
But he was denied the try as there was a Ben Foden knock-on from James Grayson's kick-off, preventing what would have been a score within just 13 seconds.
Both sides then spent the next 20 minutes searching from some inspiration, and it was Harry Mallinder who provided it for Saints.
With a penalty coming, the ball came out to the backs and Mallinder dummied Toby Flood to score.
Grayson missed the conversion and the Falcons soon responded as Sinoti Sinoti slalomed his way through to score.
Flood converted to put his team ahead for the first time and they were soon extending their lead, flying forward, with Sinoti Sinoti again leading the charge before offloading to Josh Matavesi, who scored.
Flood converted quickly again, putting his team 14-5 up and prompting frustrated groans from some home fans.
But the Saints pack soon stepped things up in the power stakes, earning their side a penalty try from a huge lineout drive.
Flood was sin-binned for collapsing the maul during that Saints move and the announcement of the former Leicester man's yellow card brought a big cheer.
Saints thought they had scored again before the break, but the TMO ruled that there was no clear or obvious grounding of the ball after Hartley headed towards the line.
The Falcons held a 14-12 half-time lead and Saints turned to England back Francis, bringing him on for Grayson at the break.
But it was the opposition fly-half, Flood, who registered the first points of the second period, with the Falcons 10 kicking a penalty.
Saints had lost the momentum they had at the end of the first period and they were now desperately searching for a spark.
But Newcastle, who were taking their time at every set piece, had come to frustrate and they were defending manfully.
Eventually Saints found their way over the line, with skipper Hartley providing a timely try for his team.
Francis converted to give Mallinder's men a 19-17 lead with 19 minutes remaining and Alex Waller soon caught the eye on his 150th consecutive Premiership appearance, making a brilliant break that almost brought another try for his team.
Ahsee Tuala looked to have bagged the bonus-point try when he dotted down, but yet another TMO review denied Saints again as there was a knock-on from Nic Groom at the breakdown.
Francis did ensure they came away with some points as he landed a penalty with 10 minutes to go.
But Newcastle started knocking loudly on the door with five minutes remaining and after a succession of penalties, Latu eventually forced his way over.
Takulua held his nerve to slot the match-winning conversion from just to the left of the posts and there were a few boos as the home faithful they showed their frustration.
Saints: Mallinder; Estelles, Horne, Stephenson (Tuala 44), Foden; Grayson (Francis 40), Reinach (Groom 61); Waller (Van Wyk 77), Hartley (c), Ford-Robinson (Hill 71); Paterson, Lawes; Wood, Gibson, Harrison.
Newcastle Falcons: Hammersley; Goneva, Harris, Matavesi, Sinoti; Flood (Hodgson 71), Takulua; Vickers (Mavinga 70), Cooper (Lawson 66), Welsh; Green (Witty 70), Robinson; Welch (c), Graham, M Wilson (Latu 60).
Referee: Craig Maxwell-Keys