In an interview with Sky Sports News, Cavendish says that he does not believe Armitstead was doping, but that "Lizzie herself could have prevented the chaos she's in."
27-year-old Armitstead competed in the Olympic road race in Rio on Sunday but could only manage fifth, having suffered through a week under the spotlight in the build up to the race as news broke of her missed tests.
Mark Cavendish, omnium elimination, Track World Championships 2016
(Image credit: Andy Jones)
"Did she dope? No, and I don't believe she did, you know," said Cavendish.
"Was it an administrative error? Yes. Was it her fault? Yes absolutely. I know from personal experience how difficult the whereabouts system can be.
"But I have an alarm on my phone every night at 6pm and my wife has one on her phone and she makes a habit of when we talk every night she will ask me 'Have you done your whereabouts?'
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The Manxman was speaking from Rio where he's preparing for a shot at gold on the track in the men's omnium which begins on Sunday, although will appear in the team pursuit on Thursday.
Cavendish himself has recorded a missed test in the past, and says that he found it "ridiculous" that an athlete that misses three tests should get a bigger sanction than an actual failure.
"I don't think it is fair that you can get a bigger sanction for an administrative failure than for an actual doping offence. It's ridiculous," he said.
"I had a missed test with the Giro d'Italia and I think the majority of sports people have a missed test...
"You are a bit blasé until you miss your first test, but missing three?
"I think Lizzie herself could have prevented the chaos that she's in but I think she's done well to deal with it, get on her bike and show why she's world champion."
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Richard is digital editor of Cycling Weekly. Joining the team in 2013, Richard became editor of the website in 2014 and coordinates site content and strategy, leading the news team in coverage of the world's biggest races and working with the tech editor to deliver comprehensive buying guides, reviews, and the latest product news.
An occasional racer, Richard spends most of his time preparing for long-distance touring rides these days, or getting out to the Surrey Hills on the weekend on his Specialized Tarmac SL6 (with an obligatory pub stop of course).
