David Luiz, Zlatan Ibrahimovic, Blaise Matuidi and Javier Pastore scored the goals that put PSG on 56 points from 28 games, two ahead of Olympique Lyonnais who can reclaim the lead if they beat Montpellier away on Sunday (8.00 p.m. BST).
Marseille are a further point back in third on 53 after thrashing Toulouse 6-1 away on Friday. Monaco are fourth on 47 after beating Evian Thonon Gaillard 3-1 away on Saturday.
PSG warmed up for their visit to Stamford Bridge for their last 16 return leg with Chelsea on Wednesday, having drawn 1-1 at the Parc des Princes, with a comfortable win over Lens.
The visitors, who reduced the arrears to 2-1 through Yoann Touzghar after 68 minutes, stayed second-bottom on 22 points having lost seven of their last 10 league games and won none.
The hosts dominated but Lens keeper Rudy Riou kept his team afloat with a string of fine saves before the northerners cracked on the stroke of halftime.
PSG went ahead when Luiz wrongfooted Riou with a low, long-range free kick in the 43rd minute as the Brazil defender netted his second league goal.
Laurent Blanc's side doubled their tally on the hour when Sweden striker Ibrahimovic converted a penalty after Gregory van der Wiel was brought down by Bapiste Guillaume.
Touzghar narrowed the deficit from close range but Lens's hopes quickly vanished.
PSG substitute Pastore had an immediate effect when France midfielder Matuidi tapped in from the Argentine's cross to make it 3-1 10 minutes from time.
Pastore wrapped it up three minutes later by volleying home Ibrahimovic's fine lofted pass in the box.
Van der Wiel almost added a fifth in the closing stages but his rising shot from the spot smashed against the bar.
Monaco lost winger Yannick Ferreira Carrasco who left the pitch with a possible ankle injury after 15 minutes at Evian and he was replaced by the Bulgarian striker Dimitar Berbatov.
The visitors took the lead in the 19th minute throgh Anthony Martial before Berbatov's 35th-minute shot was deflected into his own net by Kassim Abdallah to double Monaco's lead.
Almamy Toure made it 3-0 on the hour before former Monaco player Pape Amodou Sougou reduced the arrears for Evian, who are in 16th place three points above the relegation zone.
(Reporting by Julien Pretot; Editing by Ken Ferris)
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