Chelsea dropped their first home points of the season on Sunday when new signing Marcus Bent earned Charlton Athletic a 1-1 draw at Stamford Bridge.
That result allowed Manchester United to close the gap at the top to 14 points after Rio Ferdinand's last-minute header earned a dramatic 1-0 home win over third-placed Liverpool.
Chelsea, who had won their 11 previous home games, have 62 points from 23 games, United 48 from 23 with Liverpool on 44 from 21.
Tottenham Hotspur are fourth on 41 after their goalless home draw with Aston Villa on Saturday, with Arsenal fifth on 37 after their 1-0 defeat at Everton.
Champions Chelsea seemed on course for another regulation victory after taking the lead in the 18th minute when Hernan Crespo's goal-bound header was parried by goalkeeper Thomas Myhre and Eidur Gudjohnsen reacted quickly to score.
However, Chelsea were unable to turn their possession into clear chances against a team who had lost their last four away league games, and the home side paid the price on the hour.
Darren Ambrose picked out Bent and the unmarked striker, on as a 40th-minute substitute following his two million pounds ($3.52 million) arrival from Everton on Tuesday, looped a header over the stranded Petr Cech.
CARVALHO OFF
After Chelsea had defender Ricardo Carvalho sent off 10 minutes from time for a second booking Charlton should have won the game when headers by Marcus and Darren Bent sent Ambrose through, only for Cech to block his low shot.
Charlton also won at Stamford Bridge, on penalties after a 1-1 draw, in the League Cup last October.
Sunday was the first time the leaders had failed to win a home league game since a 0-0 draw with Arsenal in April but manager Jose Mourinho dwelled on the positives of his side's record when he spoke to reporters.
"When you arrive at the end of January and you lose your first points at home I think it's fantastic," he said.
"I know the [league] record we have with two draws and one defeat is amazing and no defeats at home is unbelievable. So this day had to arrive and I'm happy with the team and the situation.
"Ask Manchester United and Liverpool if they would like to swap places."
His two nearest rivals looked anything but champions material, cancelling each other out in a midfield-dominated clash high on commitment and effort but desperately short of goal chances.
The best appeared to have come in the 62nd minute when Ferdinand cleared a Djibril Cisse effort off the line, Edwin van der Sar saved Harry Kewell's subsequent shot and Cisse blazed the rebound over the bar.
United snatched the points when winger Ryan Giggs curled in a free kick from the left and England centre back Ferdinand rose unchallenged to head past goalkeeper Pepe Reina.
Ferdinand did not score in his first 3-1/2 years at United and has now notched three in five weeks.
