Leeds' automatic promotion hopes suffered a damaging setback as they suffered a 1-0 Sky Bet Championship defeat at Birmingham who ended a run of five straight defeats.
Blues striker Che Adams again proved to be Leeds tormentor as he scored his 22nd goal of the season in the 29th minute to earn City boss Garry Monk the double over his former club this season.
Adams also scored both goals in a 2-1 win over Leeds at Elland Road in September.
Birmingham had gone into the game on the back of a wretched run, and in the relegation battle following their nine-point penalty deduction but the win against Leeds has given their survival hopes a huge boost.
In contrast to Birmingham's recent run, Leeds had won four of their previous five games but they struggled to find that kind of form against City.
It was Leeds, though, who went in search of a quick breakthrough and they were almost rewarded after only two minutes.
Tyler Roberts raced forward from the centre of midfield to collect a ball from Patrick Bamford but pushed his shot wide.
Birmingham struggled to mount a threat of their own until the 18th minute when Jacques Maghoma forced a corner that Lukas Jutkiewicz headed over from six yards.
After what was a relatively low key start, the game suddenly exploded into life in the space of a few seconds.
Leeds looked certain to take the lead when Patrick Bamford met a right-wing cross from Luke Ayling but his shot from close range bounced off the post and into the grateful arms of goalkeeper Lee Camp.
Leeds were still digesting that miss when Birmingham surged straight up the pitch to break the deadlock.
Maghoma played a pass across the face of the Leeds area, with Jutkiewicz letting the ball roll to Adams whose low drive whistled past goalkeeper Kiko Casilla and into the far corner of the net.
Adams then had a chance to grab a second after 39 minutes when he turned Leeds central defender Pontus Jansson but his shot lacked the power to test Casilla.
The Spanish stopper was forced straight into the action again at the start of the second-half, this time beating away a shot from Jutkiewicz.
Leeds then wasted a golden chance to equalise after 55 minutes when Stuart Dallas crossed low from the right only for Bamford to lift his shot over the bar from six yards.
When Bamford finally did get an effort on target from a Roberts cross in the 69th minute he saw his header tipped away by Camp.
Although Leeds enjoyed their best spell of the game at that stage, they could easily have suffered a heavier defeat but for Casilla who twice denied Adams in the final 10 minutes.