The UMP camp claim there were 200,000 people present on the square, while several others have said it would be impossible to fit in that many people.
A tweet from Sarkozy’s personal account at 7.04 last night showed an aerial photo of the rally and said: “This May 1st, there were 200,000 of us to celebrate at the Place du Trocedero”.
But socialist Manuel Valls was one of many to take to twitter to cry foul: “The Place du Trocedero is 22,000 meters squared. Impossible to make it hold 200,000 people.[There would be]40,000 at the most.”
If the UMP figure is true, it means there would have been nine people per square meter in the crowd during the rally.
Luke Brown, the France 24 elections correspondent, who was at the Trocedero yesterday, says the size of these outdoor rallies is not supposed to be known.
“What’s interesting this time has been the non-stop inflation of the figures. Each rally is followed by another even bigger one,” he told The Local.
“The trend is new this year, and it's a means of bypassing real debate, as people talk more about the event than the issues.
“Neither Sarkozy nor Hollande will win that many people round during the rallies - they're preaching to the converted - but they're an ideal way to control the image.
“Television stations have to use the official footage - and as you saw at the Trocadero, that was a picture postcard vision of French politics."
The second round of the French presidential elections will be taking place this Sunday.