Lupita Nyong'o has hit out at Grazia magazine after it appeared to airbrush her hair off its front cover.

The Oscar-winning actress said she was not consulted by the magazine and would not have agreed to it if she had.

In an Instagram post, the 12 Years A Slave star accused the publication of "unconscious prejudice" as she posted the before and after images.

The Hollywood star wrote: "I embrace my natural heritage and despite having grown up thinking light skin and straight, silky hair were the standards of beauty, I now know that my dark skin and kinky, coily hair are beautiful too.

"Being featured on the cover of a magazine fulfills me as it is an opportunity to show other dark, kinky-haired people, and particularly our children, that they are beautiful just the way they are.

"I am disappointed that Grazia UK invited me to be on their cover and then edited out and smoothed my hair to fit their notion of what beautiful hair looks like.

"Had I been consulted, I would have explained that I cannot support or condone the omission of what is my native heritage with the intention that they appreciate that there is still a very long way to go to combat the unconscious prejudice against black women's complexion, hair style and texture."

The 34-year-old, who is from Kenya, signed the post off with #dtmh (don't touch my hair).

It comes weeks after the Evening Standard magazine apologised for airbrushing singer Solange Knowles' braids from its front cover.

Knowles, who released a song called Don't Touch My Hair, complained that her appearance had been altered.

"dtmh (don't touch my hair) @eveningstandardmagazine", she wrote on Instagram.

The journalist who did the interview later publicly disowned the article.

Angelica Bastien said she told editors to take her byline off "because they distorted my work and reporting in ways that made me very uncomfortable".

Grazia is yet to respond on the claims made by Lupita.