Barclays Premiership leaders Chelsea claimed another three points after extending their remarkable unbeaten run over London rivals Tottenham.

Jose Mourinho's side benefited from another debatable penalty decision as they secured a 2-0 success at White Hart Lane.

Chelsea have had decisions go in their favour against Liverpool and Manchester United recently and another went their way as referee Graham Poll ruled that Alexei Smertin had been fouled by Ledley King seven minutes before the break.

Frank Lampard duly struck his 50th goal in top-flight league football and, having gained the initiative, Chelsea dominated thereafter, with Lampard rounding off a notable victory with a late second.

But given Mourinho's evident dislike for diving - or, as he put it in midweek, "cheating" - the Chelsea boss will no doubt wish to review TV replays of the debatable first-half penalty decision.

While there was contact between King and Smertin, the home crowd believed the Chelsea midfielder could at least be accused of playing for a penalty as he chased Damien Duff's cross.

Chelsea nevertheless deserved their ensuing success, taking their unbeaten league run over Spurs to an incredible 30 games, spanning 15 years.

And in doing so, they also secured a Premiership record sixth consecutive victory without conceding a goal.

Ironically, it was Spurs who had earned Mourinho's wrath for 'parking a bus' in front of their goal when, under Jacques Santini, they battled their way to a goalless away draw last September.

Martin Jol has since changed Spurs' style dramatically, bringing an excellent run of results that earned him the December manager of the month award, which was presented to him before kick-off.

The home side were immediately on the attack, with Erik Edman flashing a long-range shot over the top and Robbie Keane flicking a header narrowly wide.

However, Chelsea were adept at picking off Spurs on the break, with Didier Drogba lifting a shot over Paul Robinson after beating the offside trap but seeing the ball bounce past the post.

That prompted Spurs back on the attack, with Jermain Defoe cutting inside before letting fly with a fierce shot that Petr Cech managed to parry to safety.

However, Spurs were playing with some assurance, it was still Chelsea who displayed the extra touch of class.

While captains John Terry and King both led by example as they displayed how Sven-Goran Eriksson is spoilt for choice in central defence, but King was enduring the busier afternoon.

While he produced one superb covering tackle on Drogba, keeper Paul Robinson still needed to react quickly as he twisted to push Duff's snap-shot around the post.

Arjen Robben also went down under a challenge from Noe Pamarot inside the area, bringing both sets of coaches to their feet, one claiming a penalty and the other a dive.

Referee Poll neither awarded a spot-kick nor issued a booking, but Chelsea still went ahead from the penalty spot soon afterwards despite, arguably, less evidence of an infringement.

Duff chased a seemingly lost cause before expertly keeping the ball in play by the corner flag and, having clambered swiftly to his feet, he delivered an inviting low cross.

Smertin was charging into the penalty area and, when challenged by King, he went flying to the ground and Poll did not hesitate before blowing his whistle.

Up stepped Lampard, who made no mistake as he converted the penalty with a confident shot into the bottom right-hand corner of Robinson's net.

There was some relief in the Chelsea ranks after the break, when Smertin unwittingly deflected Defoe's corner just past his own post, but the home side were short of their best up front.

Much of that was down to the superb Terry, although Drogba continued to threaten on the break, with Noureddine Naybet required to produce two well-timed challenges to halt him in full flow.

Robinson was quickly off his line to intercept on another occasion, while Drogba also headed Paulo Ferreira's excellent cross over the top.

With Fredi Kanoute out injured, Spurs were prompted to adopt the 'route one' approach in the closing stages, with King thrown up front in a bid to unsettle Chelsea's defence.

It will take more than that, however, to disrupt the best defence in the Premiership, with just eight goals conceded in 23 league games.

And it was Chelsea who looked the more dangerous, with substitute Eidur Gudjohnsen making an impact as he crossed from the byline for Lampard to strike his second in injury time.

Chelsea may have again required the 'luck of champions', as Mourinho observed recently at Anfield, but you tend to earn good fortune. And Chelsea are doing exactly that.

Teams:

Tottenham: Robinson, Pamarot (Marney 71), King, Naybet, Edman, Brown, Pedro Mendes (Yeates 78), Carrick, Ziegler (Gardner 67), Keane, Defoe.

Subs Not Used: Fulop, Kelly.

Booked: Brown, Yeates.

Chelsea: Cech, Johnson, Terry, Gallas, Paulo Ferreira, Smertin (Jarosik 70), Lampard, Makelele, Robben, Duff (Cole 80), Drogba (Gudjohnsen 76).

Subs Not Used: Cudicini, Bridge.

Booked: Duff, Johnson, Terry, Makelele.

Goals: Lampard 39 pen, 90.

Att: 36,105

Ref: G Poll (Hertfordshire).