Tour de France 2014: Vincenzo Nibali moves to reassure fans that he is performing clean after latest stage domination

The yellow jersey holder is on the verge of a maiden Tour title after a fourth stage win

Vincenzo Nibali celebrates stage 13 victory of the Tour de France (Getty Images)

Vincenzo Nibali again showed his utter superiority over the remainder of the Tour de France field on Thursday, taking his fourth stage by racing to the top of Hautacam in the Pyrenees – then moved just as quickly to assure the doubters of his cleanliness.

The Sicilian leader of the Astana team leads the race by 7min 10sec. If he holds that gap, it will represent the second-largest winning margin in 25 years, after Jan Ullrich’s victory by more than nine minutes in 1997.

Such dominance has inevitably provoked questions, particularly in this era when it seems any exceptional performance must be accompanied by the same level of suspicion. But Nibali insists that there is no reason to suggest he is anything but honest.

“If I have a lead of seven minutes, it’s not because of a great performance one day," said Nibali.

"It’s because of seconds here and there while my adversaries have sometimes gained something and paid the following day for their efforts.

“My lead is so big because I succeeded in my first goal to gain time on the cobblestones.

"It was certainly not easy to get 2 min 30 sec there. If Chris Froome had not had any problems on the pave, it would have been a difficult day for him.”

Nibali has certainly been helped by the enforced withdrawals of Contador and Froome. And his time to the summit of Hautacam was measured to be well outside those set during the sport’s darkest era of the 1990s.

Barring disaster during today’s flat stage to Bergerac and tomorrow’s 54 kilometre time trial, he will ride into Paris as the first Italian Tour de France winner for 16 years, since the ultimately tragic Marco Pantani took the scandal-ridden 1998 race.