Second-half goals from Owen Garvan and Ricardo Fuller on his debut gave Town victory and kept the pressure on the teams above the Blues in the Play-Off places.
Garvan opened the scoring four minutes after the break, sliding in Darren Currie's corner then from another set-piece, Fuller rose at the near post to head in and clinch the points.
The victory takes Blues to within five points of sixth placed Preston with Joe Royle's side travelling to Deepdale next week.
Fuller started up front alongside Danny Haynes, the teenager recovering from ankle ligament injury.
Leicester opened brightly, Stephen Hughes calling Shane Supple into action, then Iain Hume wasted a glorious chance when he shot wide from 18 yards when he could have taken the ball on.
Town's first opening came on 10 minutes, Currie's free-kick scrambled clear after Paul Henderson had failed to make distance with his punch.
Nils-Eric Johansson headed wide from a corner, then picked up the first yellow card of the game for a blatant handball.
Another Currie free-kick was headed clear by Alan Maybury while at the other end, Supple was quick off his line to deny Matty Fryatt.
Johansson's challenge inside the box on Fuller brought penalty claims from Town but referee Paul Taylor waved away the appeals with the first-half coming to and end with Richard Naylor heading over from Currie's corner.
The second-half began with a flurry of chances at both ends, Henderson saving brilliantly from Garvan's 15 yard strike, then Supple touching Maybury's left foot shot around the post.
Henderson then saved well again from Currie's strike but from the resultant corner Town edged in front, Garvan escaping his marker and sidefooting in from two yards at the back post.
Leicester were inches away from an equaliser five minutes later, Fryatt's angled shot just going the wrong side of the post.
Haynes almost got on the end of a Currie pass, Henderson smothering the danger, with Dean McDonald then replacing the frontman on 65 minutes.
Leicester introduced a double change five minutes, Elvis Hammond and Gareth Williams on for Danny Tiatto and Hughes.
Fuller's exchange of passes with Westlake saw the Jamaican international volley wide, then the on loan striker was denied by Henderson as he tried to turn and shoot on the edge of the box.
The on loan striker was then booked after an aerial challenge that takes him to five yellow cards this season and a suspension for the Preston match.
Supple clung on under Chris O'Grady's challenge before Town doubled the lead with six minutes left, Fuller heading in Currie's corner.
Jason De Vos blocked Hammond's goal bound strike from 10 yards as Leicester looked for a way back into the game but to no avail with the Foxes' miserable record at Portman Road continuing. They haven't won at Town since 1988, a run of 11 games while the victory saw Blues move up to ninth.
Town: Supple, Wilnis, De Vos, Naylor, Barron, Richards, Westlake, Garvan, Currie, Fuller, Haynes (McDonald 65). Subs not used: Magilton, Price, Sito, Proudlock. Booked: Fuller.



















