Chelsea's faint hopes of overhauling Arsenal at the top of the league surely evaporated with a shock 3-2 defeat at Aston Villa.
Hernan Crespo stabbed home the rebound after Adrian Mutu's header had beaten Thomas Sorensen and came back off the post to put Claudio Ranieri's side in front after 11 minutes.
But Darius Vassell got the home side back on level terms from the penalty spot after a foul by Mario Melchiot in the area.
Thomas Hitzlsperger (49) fired Villa in front with a typical long-range effort and just three minutes later Lee Hendrie doubled their advantage from close range.
Crespo pulled one back in the last minute but it was scant consolation.
Portsmouth gave their Barclaycard Premiership survival hopes an enormous lift with a vital victory over Birmingham at Fratton Park.
Goals from Dejan Stefanovic (45) and Lomana LuaLua (62) put the home side in charge before Stern John pulled one back for the visitors with 23 minutes remaining.
But Aiyegbeni Yakubu sealed victory from the penalty spot after Kenny Cunningham was adjudged to have handled in the area.
The victory, which took Harry Redknapp's side three points clear of the relegation zone, was sparked by the controversial end to the first half.
Redknapp and his players were furious when they were seemingly denied the opener after goalkeeper Maik Taylor handled outside the area and Yakubu fired home the loose ball, only for referee Barry Knight to call play back for the free-kick.
Taylor was sent off amid the ensuing melee but when play eventually resumed several minutes later, Stefanovic ensured justice was done by curling in the free-kick.
Wolves, however looked doomed to an instant return to the Nationwide league after going down to a late goal at home to Bolton.
Henrik Pedersen put the visitors ahead just two minutes before the interval only for Henri Camara to level seconds later.
Dave Jones' side pushed forward in search of an essential victory but were caught out in the last minute, Kevin Davies striking the killer blow which leaves Wolves six points adrift of Leeds with just five games remaining.
Manchester City remain firmly in danger after Nicolas Anelka's goal was cancelled out by Jermaine Defoe at White Hart Lane.
Anelka took advantage of some poor defending by the home side to put the visitors in front on 25 minutes, and victory would have taken them to within a point of David Pleat's side.
But Defoe equalised seven minutes into the second half to leave City just three points above the relegation zone.
At the other end of the table, Liverpool's battle for the final Champions League place took a massive blow with a home defeat at the hands of Charlton.
The home side dominated the first half but rarely looked like scoring, and they were made to pay the price when Shaun Bartlett's 63rd minute header gave the Addicks their first win at Anfield since 1954.
Middlesbrough cruised to victory over Southampton at the Riverside, goals from Juninho and Szilard Nemeth giving Steve McClaren's side a 2-0 half-time lead.
Massimo Maccarone grabbed the third before James Beattie scored a consolation for the visitors.