Facebook’s decisions over the last nine months have resulted in “serious setbacks for civil rights,” according to the damning conclusion of a two-year-long audit commissioned by the social network to review its impact on the world.

The final report, which focuses primarily on decisions made since June 2019, praises Facebook’s move to ban American advertisers from using its tools for housing and employment discrimination, and the company’s belated decision to ban explicit support for white nationalism.

But, the auditors say, many of the changes were offset by Facebook’s decision, beginning with a speech from Mark Zuckerberg last September, to “elevate a selective view of free expression as Facebook’s most cherished value”.

“Elevating free expression is a good thing, but it should apply to everyone,” the report says. “The prioritisation of free expression over all other values, such as equality and non-discrimination, is deeply troubling to the auditors.” The pivot “deeply impacted our civil rights work and added new challenges to reining in voter suppression”.

Nowhere was the new focus more clearly felt than in Facebook’s lack of action against three Donald Trump posts in May 2020. “One post allowed the propagation of hate/violent speech and two facilitated voter suppression,” the auditors write. “These decisions exposed a major hole in Facebook’s understanding and application of civil rights … Our fear was (and continues to be) that these decisions establish terrible precedent for others to emulate.

“Specifically, we have grave concerns that the combination of the company’s decision to exempt politicians from fact-checking and the precedents set by its recent decisions on President Trump’s posts, leaves the door open for the platform to be used by other politicians to interfere with voting.

“Facebook has not, as of this writing, reversed the decisions about the Trump posts and the auditors are deeply troubled by that because of the precedent they establish for other speakers on the platform and the ways those decisions seem to gut policies the auditors and the civil rights community worked hard to get Facebook to adopt.”

The audit was welcomed by Facebook’s chief operating officer, Sheryl Sandberg. “As hard as it has been to have our shortcomings exposed by experts, it has undoubtedly been a really important process for our company,” Sandberg said. “We would urge companies in our industry and beyond to do the same.”

But while the company has committed to a number of changes proposed by the auditors, including hiring a civil rights leader, banning ads that are “divisive and include fearmongering statements”, and investing $100m (£80m) in black-owned small businesses, even before the audit was published Sandberg had warned that not every recommendation would be implemented. Facebook did not give specific examples of which recommendations were to be passed by.

Farhana Khera, the executive director of Muslim Advocates, a US-based nonprofit, said that the audit “lays bare the many ways Facebook has shamefully harmed Muslims and other vulnerable communities, but even more shameful is the company’s refusal to do anything meaningful to stop this pain and violence”.

The report’s publication, which was set two years ago, coincidentally comes amid one of Facebook’s most serious crises to date: an advertiser boycott coordinated by a coalition of civil rights groups, Stop Hate for Profit, urging the company to implement a set of policies aimed at curbing hate speech on the platform.

Despite telling advertisers and colleagues that the company would not bend to revenue pressure, Zuckerberg went on to announce a series of changes as a result of the boycott, including a promise to “reconsider” a number of existing platform rules about incitement of violence. The changes were described by the auditors as “positive movement in reaction to the uproar”, but did little to please the boycott organisers themselves.

“Facebook showed up to this meeting expecting a grade A for attendance,” said Rashad Robinson, of the Color of Change, one of the coalition members. “Attendance alone is not enough. At this point we were expecting some very clear answers to the recommendations we put on the table, and we did not get that. We did not get to the heart of these problems.”