A complete mix-up between centre-backs Kenny Cunningham and Matthew Upson and goalkeeper Maik Taylor gifted the home side an early lead at the Valley when Addicks defender Talal El Karkouri scored direct from a 40-yard free-kick.
Blues equalised through Mario Melchiot early in the second half but more poor defending saw Charlton score twice more to record their first ever Premier League win against Blues on home soil.
"It was woeful defending," the Blues boss said after the game.
"At this level You can't give goals away like that.
"We've committed the cardinal sin of conceding an early goal after just 9 minutes.
"You're not going to see a worse goal for months as far as I'm concerned. It was Sunday morning stuff.
"Then after getting ourselves back in the game more niaeve defending has cost us again."
Bruce refused to criticise anyone in particular for the bizarre first goal.
"I'm never going to publicly balme anyone but my view was that Kenny Cunningham shouted to Matty (Upson) to leave it and the goalkeeper (Maik Taylor) expected him to head it.
"It's one of those horrible catastrophe's that's going to live with us for a long time. You just can't comprehend things like that.
"A lot of people will have gone away from here thinking we didn't deserve to get beat 3-1 but the one thing you have to do at this level is defend properly and I didn't think we defended at all properly today."