Iago Aspas levelled for Celta, who are fourth bottom of La Liga, shortly after the restart with a deflected strike.

But Lewandowski clinched victory from the spot, leaving third-placed Barca seven points behind Real Madrid.

Leaders Real, who travel to city rivals Rayo Vallecano on Sunday, are five points clear of second-placed Girona after they were held 1-1 at Villarreal on Friday.

Barcelona have claimed 24 points with goals scored after the 76th minute - the most in the Spanish top-flight this season.

The Catalans are also unbeaten in four matches since head coach Xavi announced he would step down at the end of the season.

Xavi's side face Napoli on Wednesday in the Champions League last 16, with the European competition being their last realistic chance of silverware this season.

Atletico Madrid are fourth, three points behind Barca, after they thrashed visitors Las Palmas 5-0 on Saturday.

Marcos Llorente and Angel Correa both scored twice for Atletico before substitute Memphis Depay added a late fifth.

The hosts recorded a comfortable victory despite Rojiblancos manager Diego Simeone resting key players - including France forward Antoine Griezmann - before their midweek Champions League last-16 tie at Inter Milan.

Elsewhere, Cadiz remain in the relegation zone after a 2-0 defeat at 11th-placed Osasuna.