Female newsreaders showing their bare arms on TV is "demeaning", Canada's first woman Prime Minister has claimed.

"Bare arms undermine credibility and gravitas," Kim Campbell wrote on Twitter.

The 70-year-old lawyer, who served as Prime Minister briefly in 1993, linked to a blog post citing a recent study suggesting people who wear more clothing are considered smarter.

In the blog, Dr Nick Morgan wrote: "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."

Ms Campbell said in her tweet: "I am struck by how many women on television news wear sleeveless dresses - often when sitting with suited men.

"I have always felt it was demeaning to the women and this suggests that I am right. Bare arms undermine credibility and gravitas!"

Her remarks drew criticism on Twitter, with some pointing out the example of Michelle Obama, the former US First Lady who regularly wore sleeveless dresses.

"She doesn't read the news!" Ms Campbell said in response.

Michelle Rempel, a Canadian MP, said: "I firmly believe in the right of Canadians to bare arms."

Others pointed out a black and white portrait of Ms Campbell showing her bare shoulders as she holds up lawyers robes.