Unfashionable Lille drew 1-1 with St Etienne on Wednesday but it was enough to guarantee they finished the year top of the French championship for the first time since 1949.
A trio of pursuing clubs failed to take advantage of them dropping two points, with PSG losing 2-0 away at Nancy, the visitors playing most of the match a man down after Mamadou Sakho was red carded and a second-half double by Youssouf Hadji giving the hosts the points.
Rennes also lost, 1-0 away at struggling Caen while Lyon were held to their second successive draw with a 1-1 draw at home to Auxerre.
All three trail Lille by a point while champions Marseille are another two points adrift as their poor recent form continued with a 0-0 draw away at Brest, leaving them with just a haul of four points from their last five matches.
Lille's prolific striker Moussa Sow had given them the lead with just under 20 minutes remaining of an evenly-fought encounter as he slotted home his 14th goal of the season past Jeremie Janot after being set up by strike partner Ivory Coast international Gervinho.
However, their joy was dimmed two minutes later as they conceded a penalty when Blaise Matuidi went down in the area as he tried to squirm past two defenders and referee Said Ennjimi had no heistation in pointing to the spot. Bakary Sako fooled former France international goalkeeper Mickael Landreau to go the wrong way to level the scores.
Despite the disappointment of drawing, Lille coach Rudi Garcia was ecstatic at finishing the year as championsip leaders and they also have a game in hand on all their rivals. "I prefer to focus on the fact we are autumn champions, and the magnificent first half of the season we have experienced," he said.
However, not all was rosy for the Lille handler. "We tried everything this evening to win, on a difficult pitch, which is beginning to worry me about how it will cope with the rest of the season. I do not know if we are champions by default. The big sides have not accrued enough points but that is the championship at the moment. I am not going to reach any hasty conclusions. We have a one point advantage but the big guns are all there."
Paris Saint Germain were always fighting against the odds once Sakho was given a direct red card in the 13th minute for a foul on Hadji by referee Anthony Gautier. Hadji it was who was to make PSG pay in full as he broke the deadlock in the 66th minute, outpacing Zoumana Camara and shooting past PSG 'keeper Edel.
The 30-year-old Moroccan international sewed up the points eight minutes from time as he pounced to beat Edel again from a tight angle after the Cameroon goalkeeper had saved from Bakaye Traore's long range shot - the victorious players were rewarded afterwards with an extra day's holiday over the Christmas break.
Marseille's disappointment at dropping further points will have doubled with a thigh injury to recent acquisition French international fullback Rod Fanni - who was only brought in from Rennes last week as a replacement for long-term injury victim Cesar Azpilicueta. And to make matters worse for the champions Charles Kabore the player who switched to the position when Fanni was taken off was sent-off five minutes from time for his seocnd booking.
Marseille coach Didier Deschamps was surprisingly upbeat despite the run his side were on. "Four draws and four points from a possible 15, is not a good sequence, but happily the other teams aren't taking advantage of it. "All things considered I believe this is a point won tonight."
Bordeaux stumbled to their fifth successive draw, though, the 2-2 home tie with struggling Lens was gained in adversity as French national captain Alou Diarra - who had scored their opening goal - was sent-off for a second bookable offence when they were trailing 2-1. However, the hosts stole a point at the end as Yoann Gouffran levelled in time added on.