Nigel Pearson's side moved to the brink of securing their return to the top flight on Friday night with a 2-1 triumph over Sheffield Wednesday at the King Power Stadium.
That made it 21 Championship games unbeaten as they moved to 89 points - two more than Cardiff won the division with last season - and meant they would be up if QPR lost at Bournemouth and Derby failed to beat Middlesbrough.
QPR lost 2-1 on manager Harry Redknapp's return to his former club, while the Rams suffered a 1-0 loss on Steve McClaren's return to the Riverside, meaning celebrations could begin in earnest for the Foxes.
Scott Arfield rescued a 1-1 draw for second-place Burnley at Watford with an 87th-minute equaliser after Troy Deeney had snatched an early lead for the home side.
Martyn Waghorn celebrated signing a permanent deal with promotion-chasing Wiganby heaping further misery on crisis club Leeds.
Striker Waghorn was on loan at the DW Stadium until Friday night when he departed Leicester to become a permanent fixture in Uwe Rosler's squad.
The 24-year-old may yet end up playing in the top flight with the Latics, who cemented their play-off spot with a 1-0 win courtesy of Waghorn's 33rd-minute strike.
Reading also consolidated their place in the play-offs when Daniel Williams produced a 74th-minute winner at Charlton.
In contrast, Nottingham Forest continued their slide out of contention after losing 2-1 to relegation-threatened Millwall at the County Ground.
Scott Malone and Lee Martin gave Millwall a comfortable two-goal cushion, before Jamie Paterson struck for a Forest side that is now five points adrift of the play-offs.
Championship basement side Yeovil gave themselves hope of surviving after prevailing 2-1 at Blackpool.
A James Hayter penalty opened the scoring before a strike from Tom Lawrence doubled the lead, at least until Elliot Grandin salvaged a consolation effort.
The result means Yeovil are now only three points adrift of safety with six games remaining.
Play-off-chasing Ipswich were beaten 2-0 at Blackburn thanks to goals from Jordan Rhodes and Rudy Gestede.
Barnsley and Brighton fought out a goalless draw, leaving the former marooned in the bottom three, while a 90th-minute strike from Joe Mason gave Bolton a 1-0 win at Huddersfield.
Birmingham thumped Doncaster 3-1 with Federico Macheda on target twice and Lee Novak completing the scoring.
- Sports & Recreation
- Harry Redknapp