Facebook Inc. plans to bolster efforts to keep hate speech off its pages amid complaints the site allowed content that encouraged violence against women, prompting companies to suspend advertisements.

Nissan Motor Co.’s U.K. unit and lender Nationwide Building Society halted some Facebook ads that could have appeared next to offensive content after the group Women, Action, & the Media criticized the social network’s response to complaints. Menlo Park, California-based Facebook said it will review guidelines for evaluating content that may violate its standards, and will update training for teams that review reports on hate speech.

Social-media services have surged in popularity by giving users leeway in posting comments, photos and videos. That freedom can backfire if members’ content pushes the boundaries of good taste, potentially turning off advertisers. The Simon Wiesenthal Center faulted Twitter Inc. in a report this month, saying that the microblogging service has helped spur growth in online forums for hate and terror.

“This should be a big concern for Facebook,” said Shailendra Pandey, an advertising analyst at Informa Telecoms & Media in London. The companies pulling advertising “are big brands and they bring in a lot of revenue each quarter.”

Facebook had $1.25 billion in advertising revenue in the first quarter of 2013, about 85 percent of its total sales. The shares fell 1.8 percent to $23.67 at 9:46 a.m. in New York.

Violent Images

“In recent days, it has become clear that our systems to identify and remove hate speech have failed to work as effectively as we would like, particularly around issues of gender-based hate,” Facebook said in a blog post yesterday. “We need to do better -- and we will.”

Women, Action, & the Media, a group that looks at gender bias, said in a letter last week that Facebook had “groups, pages and images that explicitly condone or encourage rape or domestic violence or suggest that they are something to laugh or boast about.”

As part of its effort to get the content removed, the group started an online campaign to pressure companies whose ads ran next to the images, some of which were of women who were indicated to have been beaten or raped. The effort included messages on Twitter and e-mails.

Increasing Accountability

In tweets posted on the group’s website, companies including Zipcar Inc., Zappos.com Inc. and Unilever Plc’s Dove brand responded by saying they were working with Facebook to resolve the issue. They didn’t pull their advertising, according to the group. The site reported that Nationwide, Nissan U.K. and a number of smaller advertisers did suspend ads.

Advertisers that suspend campaigns with Facebook will return when the matter is resolved because it’s an important medium for the industry, said Pandey of Informa Telecoms.

WPP Plc Chief Executive Officer Martin Sorrell has said his company, the world’s largest advertiser, spends about $270 million a year on Facebook.

Facebook plans to set up more formal communications with representatives of women’s groups and other organizations to speed up its response to questions about possibly offensive content. The company also said it will increase accountability for creators of content that is “cruel or insensitive,” even if the content doesn’t qualify as hate speech.

Nissan Dialogue

Nissan U.K. temporarily halted Facebook advertisements with demographic targeting that potentially could have shown its promotions next to the controversial content, according to Travis Parman, a spokesman for Nissan, which is based in Yokohama, Japan. Nissan wanted to have “dialogue with Facebook” to determine how its ads may have been displayed next to the content, he said. The automaker’s U.S. unit isn’t currently using the type of ad targeting in question on Facebook, he said.

Advertisements for Unilever’s Dove brand, Amazon U.K., American Express and British Sky Broadcasting Group Plc’s pay-TV brand Sky also showed up next to offensive images, according to pictures on the Women, Action, & the Media website.

“I don’t think this will hurt Facebook because in the end I think advertisers are kind of understanding that things might appear in an online environment that are unsavory, said Chris Hirst, CEO at advertising agency Grey London, whose clients include HSBC Holdings Plc, Vodafone Group Plc, and Puma SE, according to its website.

‘‘I think Facebook has been quite conscious of the environment, irrespective of advertisers, but we do add an extra layer of pressure,’’ he said.

Nationwide said it suspended all Facebook advertising and that company ads that appeared next to images depicting violence against women were linked to a user’s Facebook profile and not the pages with violent images.

‘‘Through the use of verification software, we do actively seek to ensure this type of page, or sites with suspect content, do not appear alongside our advertising,’’ the company said in a statement.