Chelsea went 14 points clear at the top of the Barclays Premiership with a comfortable victory over West Ham at Upton Park.

Second-half goals from substitute Hernan Crespo and strike partner Didier Drogba helped Jose Mourinho start the new year in style after West Ham briefly threatened to cause an upset.

Frank Lampard, who joined Chelsea from West Ham for £11million four-and-a-half years ago, was booed by the home fans every time he touched the ball.

But the England international put the champions in front when he capitalised on a mistake by Yossi Benayoun to volley home in the 24th minute of a bad-tempered London derby.

But a rare blunder from Chelsea skipper John Terry allowed Marlon Harewood to equalise just seconds after the re-start before Crespo and Drogba pounced to make the game safe for the leaders.

Chelsea knew that victory would pile more pressure on Manchester United ahead of their clash with Arsenal on Tuesday night and took the game to their hosts from the first whistle.

Not surprisingly it was Lampard who forced the first save of the match from Roy Carroll in the opening minute. The England midfielder's free-kick had to be tipped over by the former Manchester United 'keeper as the ball threatened to drop into the net.

But Chelsea suffered a real blow in the 13th minute when Michael Essien was stretchered off with an ankle injury and replaced by Eidur Gudjohnsen.

A minute later Carroll saved from Arjen Robben to prevent the champions taking the lead. Lampard had fed the advancing Asier del Horno on the left-wing and his cross was volleyed goalwards by Robben only for Carroll to save at the second attempt.

The Dutchman should have scored from such an unmarked position on the edge of the six-yard box but his effort lacked the direction required to beat the West Ham 'keeper.

But the breakthrough was not long in arriving and it was only fitting that Lampard should provide it. The Chelsea midfielder was presented with a clear shooting chance in the 24th minute when Benayoun made a complete hash of a headed clearance.

Lampard seized the opportunity in flash and sent a right-foot volley beyond Carroll to stun the home supporters.

Chelsea were now in full control and Lampard's goal merely served to underline their superiority. They almost made it two in the 35th minute when a mazy run from Robben ended with a left-foot volley from the Dutchman that Carroll did well to tip around his left-hand upright.

Two minutes later Benayoun went down following a challenge by Geremi who appeared to strike the West Ham midfielder in the face with his hand as he moved away with the ball.

Referee Webb took no action against the Chelsea defender although Benayoun required lengthy treatment before he could continue.

Minutes later Geremi appeared to strike Reo-Coker in the face with his hand a minute before the interval and Webb had to act quickly to prevent tempers from boiling over as West Ham's players vented their frustration that neither incident had been punished by the official.

Within seconds of the re-start West Ham had equalised thanks to a rare blunder from Terry. His attempted clearance was cut out by Harewood who powered his way into the penalty area before unleashing a shot which Petr Cech partially saved. However, as the ball looped towards the empty net, Harewood ran on and thumped it home to make sure.

In the 49th minute Lampard almost scored his second of the game when Damien Duff's cross landed to him on the edge of the six-yard box but he shot straight at Carroll.

Five minutes later Robben was a foot away from restoring Chelsea's lead with a right-foot shot that had Carroll scrambling along the ground to ensure it trickled past his upright.

In the 59th minute, Duff was replaced by Hernan Crespo and it turned out to be an inspired substitution as the Argentine forward made an immediate impact. Robben supplied the pass for Crespo to run on and he rounded Carroll and finished into an empty net.

Crespo should have scored a second in the 75th minute when he once again found himself clear of the home defence but he somehow put his effort wide of the far post with just Carroll to beat.

In the 79th minute, Drogba killed off West Ham's hopes of a comeback after latching on to a superb pass from Gudjohnsen with a great first touch before drilling a low shot beyond Carroll and into the far corner.

Teams

West Ham: Carroll, Dailly, Ferdinand, Collins, Konchesky, Benayoun, Fletcher, Reo-Coker, Mullins (Zamora 71), Etherington (Bellion 78), Harewood.

Subs Not Used: Hislop, Clarke, Aliadiere.

Booked: Fletcher.

Goals: Harewood 46.

Chelsea: Cech, Geremi, Ricardo Carvalho, Terry, Del Horno, Duff (Crespo 60), Essien (Gudjohnsen 13), Lampard, Makelele, Robben, Drogba, Crespo (Wright-Phillips 83).

Subs Not Used: Cudicini, Johnson.

Booked: Duff, Lampard, Gudjohnsen.

Goals: Lampard 25, Crespo 61, Drogba 80.

Att: 34,758

Ref: H Webb (S Yorkshire).