Journalist Chris Hoffman discovered Bing suggested racist topics when he looked up words such as "Jews", "Muslims" and "black people".
Bing ranked widely debunked conspiracy theories among the top suggestions for other words.
Hoffman said Microsoft had to do better at moderating its search system.
He looked up racially-themed terms and found that the majority of suggestions for further searches that accompanied results pointed people to racist sites or images.
Racist memes and images were also returned for many of the words he tried.
"We all know this garbage exists on the web, but Bing shouldn't be leading people to it with their search suggestions," wrote Hoffman.
Part of the problem is that Bing’s suggestions for further searches connected to these terms have emerged from a combination of user activity and concerted action by far-right groups to skew responses.
It was also possible to find sexual images of young girls with Bing's safety filters turned off.
The issue was like one that Google faced in 2016 by Guardian journalist Carole Cadwalladr, when she used the Google search engine to look up facts about the Holocaust.
Results for "did the Holocaust happen?" were dominated by pages denying it took place that had been created by white supremacist site Stormfront.
Jeff Jones, a senior director at Microsoft, said: "We take matters of offensive content very seriously and continue to enhance our systems to identify and prevent such content from appearing as a suggested search. As soon as we become aware of an issue, we take action to address it."