Didier Drogba took his tally to 25 in all competitions with both goals as Chelsea, without influential midfielder Frank Lampard, climbed to 61 points from 27 matches ahead of United, who lost 3-1 at Everton in a lunchtime kick-off.
NEWS: Ancelotti content with on-field performance
Dimitar Berbatov put United ahead after 16 minutes at Goodison Park, but Everton won with goals from Diniyar Bilyaletdinov (18 minutes) and substitutes Dan Gosling (76th) and Jack Rodwell (90th).
Third-placed Arsenal closed the gap on United to two points with a 2-0 home win over Sunderland. Nicklas Bendtner scored after 27 minutes and Cesc Fabregas added a stoppage-time penalty as the visitors' run without a win stretched to 13 matches.
At the other end of the table, West Ham United beat Hull City 3-0 at Upton Park to pull away from the relegation zone and leave their opponents just one point above it.
Portsmouth stayed nailed firmly to the bottom when they lost 2-1 at home to Stoke City after conceding a stoppage time goal to substitute Salif Diao - his first league strike for seven years.
Stoke were reduced to 10 men in the 73rd minute when Andy Wilkinson was sent off but took all three points after Robert Huth cancelled out Frederic Piquionne's opener for the debt-ravaged hosts.
RARE DEFEAT
Manchester United had the chance to go top, at least until Chelsea played Wolves later, if they had won but instead they suffered only their second defeat to Everton in 30 Premier League matches despite taking the lead through Berbatov.
The home side equalised almost immediately when Bilyaletdinov scored with a superb left-foot shot and clinched the points in the last 14 minutes with goals from substitutes Gosling and Rodwell.
Everton's win followed their victory over Chelsea in their last home match and manager David Moyes said: "It was a brilliant performance from the players and we are starting to get back to what we've been like for the last year or two."
Everton, who have moved up to eight place, have now lost only one of their last 12 league matches.
United manager Alex Ferguson said the defeat was a blow at this stage of the title race, a huge disappointment following their 3-2 win at AC Milan in the Champions League on Tuesday.
"We were well beaten. We were outplayed in the second half. We are going for the championship and you don't expect Manchester United to look tired like that," he said.
"It was a bad result for us at this time of year. You can't afford results like we've had today."
Chelsea capitalised on United's loss by winning at Wolves, who stay 16th, only one point above the relegation zone.
Wolves played some neat football in the early stages, but fell behind to a superbly crafted goal which Drogba scored a
