JOIN USChampions Manchester United had pulled level on points after beating a weakened Wolverhampton Wanderers 3-0 on Tuesday in manager Alex Ferguson's 900th league game in charge.
Arsenal failed to match the pace, held 1-1 by a spirited Burnley at a rain-lashed Turf Moor to move ahead of Aston Villa on goal difference in third place with a game in hand but eight points off the lead. Chelsea have 40 points, United 37 and Arsenal 32.
Nicolas Anelka put the Blues ahead in the 23rd minute in his 100th appearance for the club, slotting the ball into the bottom right corner past goalkeeper Asmir Begovic. Portsmouth refused to give in and were rewarded six minutes after the break when Jamie O'Hara's free kick hit the wall and fell for Frederic Piquionne to smash the equaliser into the roof of the net.
Lampard stepped up to lash home the 79th-minute penalty on his 300th league appearance for Chelsea.
Arsenal took the lead with Cesc Fabregas scoring with ease in the seventh minute. Burnley hit back when Graham Alexander scored from the penalty spot in the 28th minute. Liverpool, grabbed a morale-boosting 2-1 win over Wigan Athletic.