Campbell's original tweet linked to a blog post by Nick Morgan, an American communications coach, which says: "Apparently, we humans are pretty simple creatures.
"If you show up in front of us with skin exposed, we're going to think about your body. If you're wearing lots of clothing, we're going to think about your mind."
Many pointed out that Michelle Obama frequently wears sleeveless dresses, and people take her seriously, but Campbell replied that she was talking about female reporters.
Natasha Pace, a reporter, replied: "I don't believe bare arms undermine credibility. Shouldn't the audience be focusing on what is being said and not an outfit? I think people should dress how they are comfortable and what makes them feel confident. Women on TV are criticised every single day, wish it would stop."
Janice Dickinson, a political reporter, wrote: "I've worn sleeveless dresses on TV in the summer. I never got the impression that I was taken less seriously because I wasn't dressed for winter in July."
Another critic said: "I'm sorry @AKimCampbell, you may have been our first female prime minister, but this tweet just undermined your credibility of being a good role model for young women. Your words matter more than your outfit."
However, Campbell tweeted: "It is hardly sexist to care about women's credibility. This is an issue unsuited to Twitter debates."
- Telegraph Group Ltd