Tour de France leader Chris Froome had a cup of urine thrown at him while riding on the 14th stage.
Froome has been dealing with doping suspicions since hammering his rivals in the first mountain stage on Thursday.
The Brtion hit out at "irresponsible reporting" after retaining the yellow jersey following his 20th placing on stage 14, four minutes behind the winner Stephen Cummings.
It was the first stage win for Cummings, who's also of Britain.
"Unfortunately there was a bit of a dampener on the stage. A spectator, about 50-60 km into the stage threw a cup of urine at me, shouting 'doper'," Froome told a news conference.
"That's unacceptable on so many different levels. We're professionals. I think I said I would not blame the public for this, it really is a minority of the people out there, but I would blame some of the reporting on the race that has been very irresponsible.
"Those individuals know who they are, it's not all the media... there has been a lot of irresponsible reporting out there that's unacceptable."
Doping suspicions have been aired after Froome humiliated his main rivals in the first Pyrenean stage, with French TV pundits Laurent Jalabert, a former Vuelta winner, saying the Briton's performance had made him feel uneasy.
"They set the tone and people believe what they see in the media," said Froome.
Asked if he was scared by the incident and feared there could be more to come, Froome said: "I'm not scared about this, I just hope it does not interfere with the race."
It was otherwise a good day for Froome as he controlled his rivals in the finale climb of the 198.5-km stage from Rodez.
The urine throwing incident followed a report by Froome's fellow Team Sky rider, Australian Richie Porte, who claims to have been punched by a spectator during Tuesday's 10th stage.