Britain's Mark Cavendish strengthened his status as the best sprinter of his generation thanks to his third victory in this year's Tour de France in a finish marred by controversy.

Cavendish won the 184.5km 11th stage ahead of Italy's Alessandro Petacchi and American Tyler Farrar but only after his lead-out man Mark Renshaw repeatedly head-butted Farrar's team mate Julian Dean.

It was unclear why the incident took place but Renshaw, the man who usually launches the Cavendish rocket, faces being disqualified.

"Normally, he's out of the race," said Tour technical director Jean-Francosi Pescheux although the race jury's decision had not been announced.

Luxembourg's Andy Schleck retained the overall lead with a 41-second advantage over defending champion Alberto Contador.

It was Cavendish's 13th stage victory in the Tour, a performance unequalled by any sprinter in the last two decades.

The 25-year-old has eclipsed sprinting greats such as mentor Erik Zabel of Germany, Italian Mario Cipollini and Australia's Robbie McEwen.

The stage, ridden in scorching heat, was unexpectedly slow at an average of 39.8kph.