The Posh horror show began after 15 minutes when skipper Grant McCann was caught dithering in the box by Scott Wagstaff.
McCann escaped with a yellow card for hauling down the Addicks man but there was no further let-off as Johnnie Jackson scored from the spot.
Charlton only had to wait 10 minutes for a second as Therry Racon blasted home from 12 yards and Jackson completed a lightning counter-attack in the 36th minute after a Paul Benson shot had deflected into his path off defender Kelvin Langmead.
Lee Martin sealed the points soon after as he cut inside from the left flank and beat shell-shocked Posh keeper Joe Lewis with a fine finish.
A triple-substitution at the break did put some fire into Posh bellies and McCann claimed a consolation with a 25-yard free-kick nine minutes into the second period. But their defensive nightmare struck again as on-loan Lewin Nyatanga's under-hit backpass allowed Benson to feed Martin for a simple fifth on 65 minutes.