PSG, unbeaten in all competitions since Carlo Ancelotti took over as manager from Antoine Kombouare two months ago, recovered from two goals down as Montpellier, who beat Girondins Bordeaux 1-0, moved a point clear with 53 points from 25 games.
"We have mixed feelings because we cannot concede goals like that," striker Hoarau told French TV channel Orange Foot.
PSG went ahead after 21 minutes when Hoarau slotted the ball past France keeper Hugo Lloris from a Jeremy Menez free-kick.
But Lyon, who are fifth on 40 points, stormed back.
Bafetimbi Gomis volleyed home from close range in the 34th minute and Lisandro Lopez doubled their tally when he latched onto a Michel Bastos cross two minutes later.
Brazil winger Bastos then fired a 20-metre half-volley into the top corner to make it 3-1 five minutes before the break as Italian Ancelotti sat down on the bench with a vacant stare.
Nene, however, pulled one back for the visitors with a penalty three minutes into first-half stoppage-time.
Lyon made a tame start to the second half before Jimmy Briand headed home from a Bastos free-kick in the 57th to restore a two-goal advantage.
The visitors did not give up though and defender Marcos Ceara, who had just replaced Christophe Jallet, reduced the arrears on 73 minutes with a cross-shot.
UTAKA HEADER
Lloris then pulled off a couple of fine saves to deny Nene and Thiago Motta from close range but four minutes into added-time Hoarau headed in a Mathieu Bodmer cross to clinch a point.
Montpellier's match was not as spectacular but Utaka's 80th-minute header from a Marco Estrada corner saw off Bordeaux.
"We played well, we played as a team tonight," Utaka told French TV channel Foot+. "We knew it would be tricky against Bordeaux. They are a good team, it is not easy to go around their defence."
Bordeaux, who were unbeaten in Ligue 1 this year, came close in the first half when their Poland forward Ludovic Obraniak curled a shot against the post just before the break.
"We deserved to bring something back from this trip," said Bordeaux defender Marc Planus. "I am so disappointed that we conceded this goal."
Montpellier also hit the woodwork in the first half when their Morocco midfielder Younes Belhanda unleashed a shot that smashed against Cedric Carrasso's crossbar.
Saint-Etienne stayed fourth on 43 points following a 0-0 draw at AJ Auxerre who slipped a place to second bottom as Nice moved out of the relegation zone with a 1-0 home win over Caen.
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