Cavendish was competing in the individual time trial to Mont-Saint-Michel when the incident happened and Lefevere believes that the it may have stemmed from action in stage 10 when Cavendish was involved in a coming together with Tom Veelers which left the Argos Shimano rider on the tarmac after a high speed crash.
"Some spectators were not very pleased with what happened yesterday and one idiot put urine at him. Threw it at him," Lefereve said.
"Maybe you have smell his jersey before you believe," he said when one reporter asked how he could confirm the substance.
"I don’t know the taste of urine but he’s a little bit upset at the moment, and down, because he doesn’t deserve this and he’s right."
Lefereve was then quizzed on reports that Mark Renshaw will ride for Omega Pharma QuickStep in 2014, reuniting one of the most lethal leadout teams in recent history.
"I hope that Renshaw signs with me on August 1st," Lefevere said.
"Of course to help Mark, not to win races," he then added, making reference to the fact that Renshaw broke away from Cavendish in order to seek his own opportunities at Rabobank [the team later becoming Blanco and then Belkin].
"Mark calls every week with someone else but the maximum number of riders I can take is 30 and I have to look for the best people but if you look at the modern leadouts, if Mark Renshaw comes we’ll have one of the best leadouts in the world."