The defeat means Bristol stay at 11th place in the League with the threat of relegation a very real one given that they have just three games left to effect an escape.
Bristol did actually play some reasonable rugby during the first half of the match, stringing together some decent passages and maintaining their defensive discipline.
The visitors' pack looked very organised in that first 40 minutes, former England lock Garath Archer leading from the front with some typically aggressive play in the loose.
It was the second row who helped Bristol take the lead, Archer showing his worth as a ball-carrier to drive over for a try in the 23rd minute.
With Shane Drahm adding the extras and then kicking two penalties before the break, Bristol were in a 13-7 lead, Saints having fought back with a try from Spanish wing Oriol Ripol.
But, as has happened so often this season, Bristol were unable to hold onto their lead and found themselves conceding an avalanche of points against a resurgent Saints side.
The Shoguns were almost reduced to being spectators as the Saints – inspired by a tremendous forward effort – scored a total of 30 points without reply.
Fullback Bruce Reihana had a major hand in the Saints' success, scoring a try, five conversions and one penalty to dash Bristol's hopes.
There were also tries for John Sleightholme, Mark Tucker and Darren Fox, the latter touching down twice in the dying moments of the match to complete the rout.
For Northampton Saints:Tries: Fox 2, Ripol, Tucker, Reihana, SleightholmeCons: Reihana 5Pens: Reihana
For Bristol Shoguns:Try: ArcherCon: DrahmPens: Drahm 2