Floyd Landis, the one-time doper turned informant, has called for Sir Bradley Wiggins to be stripped of his 2012 Tour de France title. The American delivered a scathing assessment of the former Olympic champion and Sir Dave Brailsford, the Team Sky principal, who remained silent amid further calls for his resignation.

That came as Shane Sutton, a former Team Sky coach, turned the heat up on Wiggins and the team’s former medic to explain what drugs the five-times Olympic champion had taken and why.

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Landis said Brailsford had to take ultimate responsibility for any drugs taken by Team Sky cyclists. A parliamentary select committee report this week concluded that Wiggins, and possible support riders, had taken performance-enhancing drugs to prepare for the Tour de France under the guise of legitimately treating a medical condition. Wiggins said his use of the powerful steroid triamcinolone before three of cycling’s Grand Tours was to treat allergies and denied crossing any ethical line, as was claimed by the digital, culture, media and sport select committee report.

Landis said Wiggins would definitely have benefited from the substance. “It’s 100% performance enhancing,” the American told the Guardian. “Certain steroids increase body mass and certain ones decrease it. But they are stress hormones designed to help the body respond to fight-or-flight syndrome and increase physical ability in a life-or-death fight and that’s what cycling is. It’s undeniable it gives a performance enhancement. There’s no ambiguity.”

Landis was stripped of his 2006 Tour de France title for doping after being told of a positive test for testosterone. Some may distrust him because of his drug‑taking history even when Landis’s testimony about widespread doping in cycling contributed to the downfall of Lance Armstrong. “I don’t know what the authorities will do about Team Sky,” Landis said, “but they kicked me out and took my title for taking steroids [he tested positive for synthetic testosterone], so the same should happen to Wiggins.”

Landis, 42, believes the sponsors will walk away from Team Sky in the wake of this latest crisis. “Corporations soon won’t want to put their name next to a cycling team. If I were running a business and wanted to keep its image positive, I would have left Team Sky a long time ago.

“On top of the Froome case you put it all together and the only people who are going to try to defend Team Sky are people who still believe Donald Trump. It doesn’t matter how much you put the truth in front of their face; it makes no difference.

“It’s not going away; this is the new reality for these guys. I’ve been in this world. I know how the dynamics work and Brailsford has to take responsibility for what was going on.”

Sutton, though, said Wiggins and the former Team Sky medic Richard Freeman have questions to answer over a mystery Jiffy bag package delivered to the team at a race in 2011. Team Sky maintained it contained the legal decongestant fluimucil and not triamcinolone, as was alleged. “I have no axe to grind with Brad,” Sutton said. “My axe to grind here is Brad and the doc had a chance to come forward. They had a chance to defend Dave Brailsford and it should have been them in front of the committee. I am calling for him and the doc to come forward now and tell the truth.”

Froome, meanwhile, has rubbished the select committee report. He is preparing for the Tirreno-Adriatico race in Italy, his second competition since news of his adverse drug test was made public. But he was again facing questions about doping following the report. The MPs concluded that triam-cinolone was used to prepare Wiggins “and possibly other riders supporting him” for the 2012 Tour de France. But Froome, who has won the Tour four times, rejected any such association when speaking to reporters in Italy.

“I’ve never seen anything like that. It’s not my experience within the team that that’s how the team operates,” he said. Asked whether he was part of the Team Sky riders prepared the same way as Wiggins for the 2012 Tour de France, Froome replied: “No. That’s absolute rubbish. I’ve seen that accusation but no, that’s complete rubbish.

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“I can only speak from my own experiences in the team. I’ve been there for eight years, since day one. I certainly have a very different picture to what’s been painted in the headlines. I’m proud to be part of the team. I wouldn’t have stayed so long, I wouldn’t have been in the team, I wouldn’t still be in the team, if I didn’t believe in the team and the people around me. Dave B [Brailsford] has brought all those people together and we’ve got a fantastic group.”

Froome said he will not let anything deflect his focus from racing. “That’s part of something I’ve been dealing with over my whole career as a pro cyclist. I’ve come up against adversity and I’ve learnt how to compartmentalise things. Right now I’m here to race Tirreno and I’m focusing on that.”