WikiHow has issued an apology after a cartoon for an article on how to become a congressman depicted Beyonce, Jay-Z and Barack Obama as white people.

The how-to website publishes crowd-sourced articles on a variety of subjects.

Its tutorial on becoming a congressman featured a cartoon version of a photograph taken at a fundraising event in New York in 2012, which portrayed all three individuals as white.

A Beyonce fan account shared the two images for comparison on 22 January with the caption: "Wikihow turned Obama, Beyonce and Jay-Z white to explain 'How to become a congressman'."

At the time of writing the post had been retweeted more than 18,000 times and 'liked' 23,700 times.

A wikiHow representative tweeted from its official account and called the cartoon "disgraceful".

A fuller statement later read: "When we saw the whitewashed image of Obama, Jay-Z and Beyonce, we were disgusted and ashamed. It should never have been on wikiHow.

"Within minutes of the first tweet, a volunteer removed the image. We then started investigating how it got on wikiHow at all."

The statement claimed that the illustration was made 3 years ago by a team of illustrators "who work as one - one person sketches, the other person colours.

"The sketcher sent the colourist a black and white sketch," is said. "The colourist did not know the race of the models."

Wikihow said that the colourist was not aware that the people in the image were Obama, Beyonce or Jay Z, and that it did not believe that the illustrator had deliberately whitewashed them.

"This doesn't excuse the fact that we hosted a terrible image on wikiHow and we needed more diversity on that article," the statement added.

"We are talking with our illustrators to prevent recurrence and encourage diversity. Especially in positions of power."

The Guardian noted that wikiHow is infamous for its bizarre range of illustrations that accompany how-to articles.