(CNN) -- Chelsea missed the chance to open up a six-point lead at the top of the English Premier League as they were held to a 1-1 draw by struggling West Ham at Upton Park on Sunday.
Frank Lampard rescued a point for Carlo Ancelotti's misfiring team with a three times taken penalty after Alessandro Diamanti had put the Hammers ahead just before the interval from a spot kick.
Referee Mike Dean ruled out Lampard's two previous attempts because players had run into the penalty area before he took his kick.
But the England international midfielder kept his nerve against his old club to make it third time lucky.
The penalty award, given at the instigation of the linesman, was also hotly disputed with West Ham defender Matthew Upson appearing to play the ball first in a challenge on the returning Didier Drogba.
West Ham manager Gianfranco Zolo criticized Dean's decision in his post match interview, saying it had cost them a deserved three points.
"I think we did enough to win but you have to understand that the big clubs take advantage of everything and the penalty they were awarded was a case in point," he told Sky Sports.
"I was disappointed that the referee trusted the linesman's view, but he was closer and should have kept to his first decision," he added.
It was another unconvincing display from Chelsea, who have won just once in their last six matches in all competitions.
They offered little in the first half and fell behind as Ashley Cole fouled Jack Collison with a rash challenge in the penalty area.
Diamanti sent Petr Cech the wrong way with the spot kick, but it was clear Chelsea would improve after the break and they drew level just after the hour mark.
But West Ham still pressed for a win and Cech had to be alert to keep out Diamanti's sharp effort.
The point leaves Chelsea with 41 points from 18 games, with Manchester United, beaten 3-0 by Fulham on Saturday, on 37 and Arsenal third on 35, but having played a game less. West Ham have 15 points, one more than bottom club Portsmouth.
In Sunday's other games, Wolves beat Burnley 2-0, justifying manager Mick McCarthy's decision to play a virtual reserve team in the midweek loss to Manchester United.
Suitably rested, his first teamers responded with goals from Nnad Milijas and Kevin Doyle to gain a much-needed three points.
Biimingham's five-game winning run was ended in a 1-1 draw at Everton as Diniyar Bilyaletdinov fired Everton ahead in the fifth minute but Sebastian Larsson equalized in the 22nd.
But Birmingham moved above stuttering Liverpool into seventh place and are unbeaten in nine games.