QPR's woes continued as Tahith Chong's early goal gave Birmingham a 1-0 victory at Loftus Road.
Rangers, hammered 6-1 at Blackpool in midweek, have now lost seven of their past eight matches - and three of their four since Gareth Ainsworth took over as boss.
Since topping the Sky Bet Championship in October, their dismal results have seen them slump to just six points above the relegation zone.
Just as they did at Blackpool, Rangers conceded in only the third minute, with the poor defending which has plagued their season evident yet again.
Reda Khadra went past Albert Adomah and played in Juninho Bacuna, who pulled the ball back from the left for Chong to apply the finish from near the edge of the six-yard box.
Ainsworth - QPR's third manager this season, following the departure of Michael Beale and sacking of Neil Critchley - has installed a much more direct style than his predecessors.
Rangers launched the ball forward at every opportunity but struggled to create clear-cut chances, although Lyndon Dykes fired over after being found by Adomah's low cross and, after the interval, Jimmy Dunne's back-header was kept out by Blues keeper John Ruddy.
Birmingham comfortably coped with their opponents' route-one tactics and very nearly doubled their lead on the hour mark.
Adomah attempted to volley clear Chong's right-wing free-kick but instead sliced the ball towards Lukas Jutkiewicz, whose header was tipped onto the post by keeper Seny Dieng.
The introduction of Stefan Johansen at least gave Rangers a touch of creativity and the Norwegian's 68th-minute corner was headed wide by Rob Dickie.
But that was a rare scare for the visitors, who defended well and deserved to take the points.
While QPR remain in danger of relegation, Birmingham's win took them nine points clear of the drop zone, leaving them virtually safe.
Ainsworth will hope to get some of his key players back after the international break.
The unavailability of several of the squad, including playmakers Ilias Chair and Chris Willock, has been a major factor in Rangers' decline.
And there was another injury blow when Osman Kakay - a right-back playing as a makeshift left wing-back - was forced to go off at half-time.
There were a couple of late chances for the hosts, with Dunne heading wide and Dykes failing to find the target after a scramble in the box.
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