Birmingham - QPR's survival bid suffered a significant setback after Graham Dorrans's fine first-half goal earned West Bromwich Albion a 1-0 victory at The Hawthorns on Saturday.
Dorrans's long-range strike mid-way through the first half handed the Baggies only their second win in seven matches as they moved onto 42 points to guarantee a third successive Premier League campaign for the first time in their history.
For Mark Hughes's team, the wait for a first away win since beating Stoke City on November 19 goes on and, while they remain outside the bottom three, they lead 18th-placed Bolton Wanderers by just two points, having played two more matches than Owen Coyle's side.
West Brom were forced into a change even before a ball had been kicked after Jonas Olsson sustained a groin injury in the warm-up.
England Under-21 international Craig Dawson was drafted in as his replacement and, when the rookie defender failed to intercept an early Rangers through-ball, he had goalkeeper Ben Foster to thank for darting quickly off his line to block Bobby Zamora's attempt.
The Baggies threatened for the first time six minutes later when Marc-Antoine Fortune pinched possession from Shaun Derry before slipping in Peter Odemwingie but, from a narrow angle, he could only fire past the post.
However, Roy Hodgson's team took a 22nd-minute lead and it arrived in some style when Scotland international Dorrans unleashed an unstoppable strike into the top-left corner from 25 yards, having been teed up by Peter Odemwingie.
Opportunities went to waste at either end, with Odemwingie and Samba Diakite both shooting into the side netting, then a surge of pressure from the visitors late in the half culminated with Zamora heading a hanging cross from Jamie Mackie narrowly wide.
Just a minute later the former Fulham forward brought down Taye Taiwo's raking diagonal pass superbly only for Foster to make another fine save, blocking Zamora's shot.
Mackie threatened once more in the 44th minute when he cut inside, only to see his scuffed shot creep past the left post with the wrong-footed Foster beaten.
The Baggies almost doubled their advantage 10 minutes after the restart when Billy Jones and Odemwingie exchanged passes neatly to leave the right-back with a sight of goal 10 yards out, yet his effort came back off the foot of the post.
Joey Barton threatened with a curling attempt that narrowly cleared the Albion crossbar on the hour mark and the QPR captain came to his team's aid soon afterwards with a block to deny substitute Shane Long.
Rangers were guilty of profligacy once again when Adel Taarabt picked out the unmarked Zamora with a cutback, yet the striker's skewed shot deflected off Mackie and away to safety to complete a frustrating afternoon for the West London side.