Airbnb is working to tamp down mounting charges that some hosts on its platform discriminate against guests based on race.

Critics of the service have seized on the bias allegations, launching a campaign last week in which a woman who identifies herself as black speaks in a voice-over about how hard it is to find lodging on the home-sharing website.

{mosads}“I get declined all the time on Airbnb,” she says. “Hosts would have one excuse or another, like, ‘Oh, it was just booked or I haven’t updated the calendar,’ but their excuses don’t matter.

“I mean, Airbnb should be doing more to stop racial discrimination — because we deserve better.”

Her story is a composite of different accounts and news reports, according to Share Better, the New York-based coalition behind the ad. The group includes elected officials and housing groups, and has the support of parts of the hotel industry and unions that represent hotel workers.

The group is airing its ad on CNN, MSNBC and local outlets in six cities, including New York, Chicago and Los Angeles. An additional digital push is putting the campaign in front of more people on social media and through traditional display advertising.

“Given Airbnb’s history of ignoring laws that protect affordable housing, it’s not surprising they would sit on the sidelines while people’s civil rights are violated,” said a Share Better spokesperson in a statement. “Their lack of a proactive approach to address this widespread discrimination is a prime example of Airbnb putting their bottom line ahead of what they can and should be doing to follow both the letter and spirit of the law.

“It’s disturbing that it took a social media driven initiative to get a 21st century tech company to finally react to the kind of racial bias that wasn’t even acceptable last century.”

An Airbnb spokesperson fired back against the group, saying after the ad first aired that it was “unfortunate that the hotel lobbyists continue to mislead people about Airbnb, but we know our platform unites people from different communities and cultures and we’re going to keep working to bring people together.”

Airbnb has drawn the ire of traditional hotel operators, who see the startup as a potentially dangerous competitor.

“Traditionally, new supply has been a cause for concern for existing hotels,” said Jamie Lane, a senior economist at real estate research firm CBRE. “They have to lower rates to keep competing to bring in those customers and that is something that can reduce the profitably of existing hotels.”

This has been especially true in markets where Airbnb has had a significant presence.

The industry-aligned groups are taking advantage of controversy that began on social media, where Airbnb users spoke up about their experiences under the hashtag #AirbnbWhileBlack.

“Declined, Declined, Decline,” wrote one user on Twitter. Another man recounted on Medium how a host who repeatedly canceled his booking requests later accepted a request for the same dates from one of his white friends.

Airbnb has responded with a slate of initiatives that it says will address the concerns and improve the experience for nonwhite users.

CEO Brian Chesky addressed the allegations himself at a conference produced by the company on Wednesday, which also featured a panel on diversity.

The company last week said it would spend the summer reviewing the way guests and hosts deal with each other and brought on a former American Civil Liberties Union staffer to lead the effort.

“Airbnb leaders from every level of the company — from our product, policy, legal, and diversity and belonging teams — are focused on this issue,” the company said in a memo to individuals and organizations interested in the allegations.

Airbnb’s director of diversity, David King, said in May that the company would start offering unconscious bias training for its hosts and take other steps to combat discrimination. On Monday, the company announced a new program to help people from underrepresented groups to transition into a career in tech.

Rep. Eric Swalwell (D-Calif.), who leads Congress’s Sharing Economy Caucus, said in a statement last month that bias, “whether conscious or unconscious, must be a constant concern for any sharing-economy company.”

“Any discrimination must be addressed immediately and decisively,” he said.

A trade group that represents Airbnb and other on-demand economy companies in Washington defended the firm’s efforts to deal with discrimination.

“Internet platforms work tirelessly to ensure that they are free of discrimination and open to all users,” said Noah Theran, a spokesperson for the Internet Association. “These are issues that transcend the online and offline worlds, and Airbnb has made it clear that they do not condone discriminatory behavior in any way.”

The controversy has been an ongoing problem for the roughly $25 billion company.

In December, three Harvard University academics said they had found “widespread discrimination” against black guests on the platform. An Airbnb spokesman said at the time that the platform had a “zero tolerance” policy for discrimination and that the company was in touch with the authors of the study.

But the issues have persisted. On Monday, the company said it would ban a host for discriminating against a transgender woman a year prior. And last week, a woman said on Twitter that a host in North Carolina had canceled her reservation and, in a message, used a racial slur.

“The incident in NC was disturbing and unacceptable,” Airbnb CEO Brian Chesky tweeted the next day. “We have permanently banned this host.”