The 32-year-old triple Olympic champion kept a lead of two minutes five seconds from compatriot and Team Sky colleague Chris Froome after the 226-kilometre 12th stage from Saint-Jean de Maurienne to Annonay-Davezieux and later confirmed he had been struck by a flare.

“I’m covered in yellow stuff at the moment,” said Wiggins, who will wear the maillot jaune for a sixth day on tomorrow’s 217km 13th stage from Saint-Paul-Trois-Chateaux to Cap d’Agde, on the shores of the Mediterranean.

“I got hit on the arm with a flare at 25km to go. It burnt my arm a bit, but other than that it was all right.

“There were quite a few guys running up the hill with lit flares in the peloton.

“It was pretty dangerous and I’m sure those guys are nursing a few wounds tonight because there were quite a few bottles thrown in their direction from the peloton.”

Having survived that assault, Wiggins then faced further inquisition on the topic of doping in cycling.

With numerous instances of Tour winners having tested positive or been placed under investigation for drugs offences, the race leader is often asked for their opinion on the matter.

Wiggins launched an emotional, expletive-laden rant when questioned after his opening day in the yellow jersey on Sunday, before a more considered response followed after Wednesday’s 10th stage.

Wiggins has long been an anti-doping advocate, but felt he should not have to justify himself just because he was wearing the maillot jaune.

However, now he appreciates the need to better articulate his anti-doping stance, given the spectre of doping in the sport.

After writing a blog for www.guardian.co.uk today, Wiggins was asked to expand upon his thoughts as he seeks to become the first British winner of the Tour on July 22.

He added: “I started to understand from certain parts of the media as to why those questions are asked and I started to accept it a little bit.

“It’s all right me sitting up here and saying ’I don’t want to talk about it, I’ve said what I have to say about it’.

“But if I am to be in this position now for another week, let’s hope, and then beyond next season trying to do it all again, there’s no point in me sitting and swearing every time that question gets asked.

“It hurts me. I take it very personally. Perhaps I shouldn’t take it personally, perhaps it’s just a position our sport is in from people who have set a precedent, sat in this position before me.

“I do want to start building bridges to prove that I’m doing this off of bread and water and hard work and nothing else.

“If I can be as open, as honest as possible, hopefully that will go some way to people believing that what I’m doing is honest and off of bread and water.”

Wiggins insists his stance has not changed since the 2006 Operacion Puerto scandal and 2007, when he was embarrassed to be a member of the Cofidis team expelled from the Tour when Cristian Moreni tested positive.

He emphasised what he has to lose – his reputation, his family – using the metaphor of a hand full of sand, which would slip through his fingers.

In his blog, Wiggins was critical of some now-retired riders who remain revered despite previous doping convictions.

But he believes cycling is cleaning up its act and praised Millar, who served a two-year ban from 2004 to 2006 for admitting using banned blood-booster EPO but is now a fervent anti-doping campaigner, for playing his role in proceedings.

Wiggins said: “I think Dave is one of the very few exceptions, because of what he’s stood for since he came back into this sport in 2006.

“He’s tried to do something and help change the future of this sport.”