Twitter Inc. today issued an apology after an investigation revealed that it allowed keywords such as “neo-Nazi” and “white supremacist” to be used to target users on the platform.

The results of the investigation were published today by the BBC, which said that other words such as “anti-gay” and “transphobic” could also become part of an ad campaign.

Advertisers can choose any number of keywords to reach a certain kind of audience, but according to Twitter’s terms of service, words or phrases relating to hate speech aren’t allowed. This falls into the area of “sensitive categories” according to Twitter’s policies. These categories include things such as “racial or ethnic origin,” “sex life” and “political affiliation or beliefs.”

“Twitter allows ads to be directed at users who have posted about or searched for specific topics,” said the BBC. The people who the BBC reached in its investigative campaign might not necessarily be racist or transphobic, but being able to used such phrases could be problematic in terms of building an audience.

Using an ad tool, the investigation revealed that if the term “neo-Nazi” were used in the U.K., the ad could reach 67,000 to 81,000 people. For the cost of just a few pounds, the BBC found that if it used the keywords “islamophobes,” “islamophobia,” “islamophobic” and “#islamophobic,” the potential reach was 92,900 to 114,000, according to Twitter’s ad tool.

The BBC also tried to reach 13- to 24-year-olds with the keywords “anorexic,” “bulimic,” “anorexia” and “bulimia.” Twitter’s ad tool said that could reach about 20,000 people. After 255 people saw the ad and 14 people clicked on it, it was pulled. The problem in this regard is companies trying to sell weight loss products and dietary supplements.

“We’re very sorry this happened and as soon as we were made aware of the issue, we rectified it,” said a Twitter spokesperson. “[Our] preventative measures include banning certain sensitive or discriminatory terms, which we update on a continuous basis. In this instance, some of these terms were permitted for targeting purposes. This was an error.”

Image: Andreas Eldh/Flickr