Posh overcame the division's in-form team in fine style at the Weston Homes Stadium on Saturday afternoon.
A crowd of over 10,000 were treated to a superb Peterborough United display as Darren Ferguson's men overcame the division's most in-form team in comprehensive fashion and in truth, it could have been six or seven with Posh missing a host of second half chances.
Those chances ultimately didn't cost Posh as they ran out 3-0 winners over the Addicks to move nine points clear of the drop zone with a better goal difference.
Former Posh striker Matt Godden had the first opportunity of the game, but he dragged a shot wide of the post via a deflection.
Lloyd Jones hit the crossbar with a looping header a minute later before the same man was cautioned for a foul on his namesake Ricky-Jade Jones.
Mothersille curled a shot over the top after good approach play including a silky nutmeg from Abraham Odoh on 18 minutes.
On 35 minutes, Posh had a unique chance to break the deadlock as an indirect free kick was awarded in the penalty area after a backpass to Will Mannion.
Posh didn't score from the resulting set-piece as Mothersille's shot was blocked but the ball was recycled back to Kwame Poku and his fine delivery was headed into the corner by Sam HUGHES for his first goal of the season in a Posh shirt.
On 43 minutes, Posh doubled their lead and it was a fine counter-attack with Jones finding Mothersille and he picked out ODOH who curled the ball into the corner with his right-foot.
Docherty and Godden went close early in the second half before Posh had a chance to make it 3-0 as Jones and Mothersille combined to create a chance for Odoh who fired over.
Substitute Aneke headed over from a deep cross while Steer did well to gather a low strike from Ramsay from 20-yards.
On 58 minutes, a fine clearance from Steer found Mothersille, but he couldn't force his half-volley past Mannion.
Johnson saw a shot blocked after good work from Mills before Posh carved out another huge chance on 64 minutes as Hayes picked out Mothersille, but he blazed over from 10-yards.
Odoh was then superbly denied by Mannion from close-range as another chance went begging with Jones also finding the side-netting moments later from an acute angle.
The third goal did finally arrive on 79 minutes as Hayes did well down the right and squared for MOTHERSILLE who this time made no mistake.
With a minute to go on the clock, Steer made two good saves to preserve the clean sheet with Harley Mills going close to a fourth deep in stoppage time.
Posh: Steer. Collins, Wallin, Mothersille (sub Fernandez 82min), Odoh, Poku (sub Hayes 53min), Jones, Susoho (sub De Havilland 82min), Hughes, Dornelly (sub Johnston 61min), Mills. Unused subs: Bilokapic, De Havilland, Conn-Clarke, Katongo.
Charlton: Mannion, Ramsay, Gillesphey, Jones, Coventry (sub Ahadme 82min), Campbell (sub Anderson 82min), Berry (sub McIntyre 68min), Docherty, Godden (sub Gilbert 68min), Small, Watson (sub Aneke 53min). Unused subs: Bouzanis, Enslin.
Half-time: Peterborough United 2-0 Charlton Athletic
Full-time: Peterborough United 3-0 Charlton Athletic
Attendance: 10,231 (2,764 Charlton fans)
Referee: S. Tallis