Jose Mourinho's side can no w clinch the league against Crystal Palace on Sunday and claim their first crown since 2010
They are 13 points clear of Manchester City and Arsenal with just four games left, although the Gunners have a match in hand
Didier Drogba, John Terry and Ramires scored second half goals to rescue the visitors after d isciplined Leicester had shocked them - Marc Albrighton's first goal for the club gave the hosts a deserved lead
The Foxes, one point above the bottom three, matched Chelsea in a dogged and organised display despite being denied a fifth straight top flight win for the first time since 1963/64.
Drogba started for Chelsea along with Petr Cech - with Oscar, after his head injury at Arsenal, and Thibaut Courtois, who was struggling with a hip injury, on the bench
Diego Costa missed out, not risked after a hamstring problem.
Leicester were unchanged as Jamie Vardy started despite being a doubt with a foot injury.
The hosts began well, snapping at their sloppy visitors who were not allowed to settle with Esteban Cambiasso pulling the strings.
The midfielder, central to Mourinho when they won the Champions League at Inter together in 2010, created a fine opening for Ulloa with a glorious pass on 12 minutes, only for the striker's touch to let him down.
Drogba then failed to connect with Willian's cross as Chelsea threatened before Eden Hazard's excellent pass unlocked the Foxes, only for Cesc Fabregas' cross to be hacked clear.
The leaders started to probe and Leicester suffered a double blow in a matter of minutes as Andy King, on his 300th appearance for the club, and former Chelsea defender Robert Huth were forced off.
Matty James and Ritchie De Laet replaced them but it failed to hurt the Foxes' resilience as they held off Chelsea with a degree of ease.
While the visitors pressed they rarely looked like making a breakthrough against the organised hosts.
Danny Drinkwater fired over seven minutes before the break and the leaders then survived a huge scare moments later.
Albrighton's cross was met by Paul Konchesky, who saw his shot turned against the post by Cech and then his cross half-cleared.
James headed the ball back for Cambiasso and his lay-off found Albrighton, whose goalbound shot was blocked.
But the winger scored his first goal since January 2012 in first half stoppage time to send the home fans into raptures.
James sent Vardy scampering down the left and, when he crossed, Cesar Azpilicueta slipped and Albrighton passed the ball into the corner at the far post.
The King Power Stadium erupted but was left in stunned silence three minutes after the break when Chelsea levelled.
Leicester had been controlled at the back but allowed Branislav Ivanovic to squeeze down the right and cross for Drogba to sweep in from 10 yards.
Two minutes later the striker, who had been poor in the first half, fired over and then Fabregas failed to connect with Willian's sumptuous centre.
Chelsea had upped their game and Drogba flashed a shot wide after 62 minutes as Leicester struggled to match their first-half tempo.
James saw a shot deflect wide but the visitors were in the ascendency and went ahead 11 minutes from time.
Kasper Schmeichel produced an excellent save from Gary Cahill's header, only for Terry to bundle in the rebound.
And four minutes later it was 3-1 when Fabregas cut the ball back for Ramires to find the top corner from 18 yards.
Source : PA
Source: PA