|Northampton (3) 25|
|Tries: North, Horne, Haywood Cons: Francis 2 Pen: Francis Drop-goal: Francis|
|London Irish (14) 17|
|Tries: Lewington 2 Cons: Tonks 2 Pen: Tonks|
Northampton scored three tries in just eight minutes at the start of the second half to turn around a half-time deficit and beat London Irish.
They trailed 14-3 at the break after Alex Lewington's two tries for Irish, but a burst of scores turned the game.
George North finished a move he began before Luther Burrell put Rob Horne in, and after a 30-yard maul, another heave drove hooker Mikey Haywood over.
Greig Tonks' boot kept Irish in it but they could not secure a bonus point.
The defeat, and Worcester's victory over Gloucester, moves Irish perilously close to relegation with a home game against the Warriors to come next week.
Nick Kennedy's side are now 16 points behind Worcester with seven matches remaining.
Irish took a healthy lead at Franklin's Gardens thanks to Lewington's finishing prowess.
First, he gathered his own kick ahead to score the game's first try and then after Tonks put a grubber into the in-goal area, the winger seized on North's hesitation to touch down for his second try.
It left Northampton needing a second-half response and they found it instantly as Wales wing North claimed the kick-off, scored from the subsequent move and sparked Saints into life.
Piers Francis slotted a drop goal to stretch the lead beyond a single score and ensure Saints' sixth win of the season to end any relegation worries.
London Irish director of rugby Nick Kennedy told BBC Radio Berkshire:
"I thought we played very well in the first half, we were full of energy, full of enthusiasm. It was a few errors from us in different areas that cost us after the break.
"That eight-minute spell was a big momentum swing. Those little switch-offs and tiny areas have cost us big this season and they've cost us today.
"It's completely my responsibility and we're going to fight right to the end until it's mathematically impossible.
"Most people are writing us off now, so there's no pressure on us and we just need to go out and play."
Northampton: Tuala; North, Horne, Burrell, Foden; Francis, Groom; Ma'afu, Haywood, Brookes, Ratuniyarawa, Day (capt), Gibson, Brussow, Harrison.
Replacements: Marshall, Van Wyk, Ford-Robinson, Ribbans, Wood, Reinach, Myler, Tuitavake.
London Irish: Marshall; Cokanasiga, Fowlie, McLean, Lewington; Tonks, Van Zyl; Franks, Paice, Hoskins, Van der Merwe (capt), Paulo, Botha, Northcote-Green, Treviranus.
Replacements: Porecki, Elrington, Du Plessis, De Chaves, Gilsenan, Steele, Bell, Tikoirotuma.
Referee: Ian Tempest.