Goals from Jordan Stewart followed by second half strikes from Paul Dickov and Marcus Bent sealed the points for The Foxes in a game City never looked likely to get anything out of.
Joey Barton had two efforts in the opening ten minutes both on his right foot, one went harmlessly wide but his second attempt forced Ian Walker into a smart save.
The visitors then began their scoring when referee Mike Riley played a good advantage when Dickov was pulled down and Stewart broke forward and with no support arriving on his right decided to take aim and curl a superb left foot effort around the despairing Kevin Stuhr-Ellegaard on 12 minutes.
Nicolas Anelka and Steve McManaman showed a sign of what was to come for City when they both attempted to connect with Michael Tarnat's cross and only succeeded in sending the ball out for a goal kick on 40 minutes.
Leicester were awarded a penalty five minutes into the second half when Dickov held the ball up in the area and Sylvain Distin tackled him from behind. There was little wrong with the challenge but when Dickov got up to confront the Frenchman he stuck out an arm to leave the Scotland international in a crumpled heap.
Riley immediately blew to signal a penalty and former City boy Dickov comfortably slotted home Leicester's second.
Five minutes later Bent made it 3-0 when he beat Sun Jihai to a Muzzy Izzet cross from the right and he should have netted a second on the hour mark when Izzet again crossed from the left, but Bent could only find the side netting.
Matters failed to improve when Anelka wasted another chance when McManaman played a ball over the homeside's rearguard but the former Arsenal marksman pulled his left-foot effort just wide.
Anelka then headed over from a Distin flick on from a corner, but the luckless striker's form in front of goal summed up City's woeful night as Kevin Keegan's side suffered their second home Premiership defeat of the season.
