Enzo Maresca’s league leaders lost to goals from Ilias Chair and Sinclair Armstrong – with his first touch after coming on – either side of half-time.
The Foxes pulled a goal back through Ben Nelson, but could not find an equaliser as QPR gained a third straight win.
Leicester are just three points ahead of second-placed Ipswich and five in front of third-placed Leeds with 11 games remaining.
The top two are promoted automatically to the Premier League, with the teams from third to sixth going into the play-offs.
Leeds were denied a 10th successive league win in a 1-1 draw at 10-man Huddersfield.
Patrick Bamford’s second-half equaliser salvaged a point for Leeds following Michal Helik’s opener.
The relegation-threatened Terriers lost captain Jonathan Hogg to a second yellow card in first-half added time for swinging an arm at Junior Firpo.
Ipswich took advantage to seize second place thanks to a 2-0 victory against Plymouth.
Brendan Galloway’s 63rd-minute own goal broke the deadlock at Home Park before Kieffer Moore’s fifth goal in seven games sealed the Ipswich victory.
Joe Aribo hit a stoppage-time winner as fourth-placed Southampton snatched a 4-3 win at 10-man Birmingham.
Adam Armstrong, David Brooks and Che Adams netted as Saints twice coming from behind to lead after goals from Birmingham’s Koji Miyoshi and Jay Stansfield.
Juninho Bacuna appeared to have earned the struggling Blues a point following the 62nd-minute dismissal of Dion Sanderson, but Aribo pounced with just seconds left.
Ike Ugbo’s sixth goal in five games gave second-bottom Sheffield Wednesday a 1-0 win over bottom-of-the-table Rotherham at the New York Stadium.
Millwall clinched a second successive win since the return of manager Neil Harris thanks to Zian Flemming’s third-minute free-kick in a 1-0 victory against Watford at The Den.
Stoke are third bottom, level on points with the three teams above them, after strikes from Bae Jun-ho and Lewis Baker secured a 2-0 win against Middlesbrough.
Blackburn lost 2-1 at Swansea, while Cardiff beat Bristol City 1-0 at Ashton Gate.
Norwich beat Sunderland 1-0 and Preston played out a goalless draw with Hull.
AFP
