Facebook staff say discrimination has got worse since a black former employee claimed last year he had witnessed a range of issues within the company.
The anonymous group of tech workers at the social media giant penned a letter describing the alleged discrimination experienced by 12 current and former employees of colour, including black and Latino workers.
In one situation described by the group, a programme manager was reportedly asked by two white employees to clean up their mess and told to "dress more professionally" when the issue was raised with a senior manager.
Another worker is said to have told of how managers would deliberately provide negative feedback on their performance.
The group also accused Facebook of creating a hostile culture "where anyone who is non-white is made to feel fear for their job", which is why the letter has remained anonymous.
It comes almost a year after former Facebook manager, Mark Luckie wrote a letter saying black employees faced discriminatory comments and were often "aggressively accosted by campus security".
The letter read: "Since Mark Luckie’s brave post nearly one year to this day highlighting the patterns of aggression against black employees, not much has changed. There may be a few more posters on the wall. There may be an effort to recruit diverse talent. But not much has changed to ensure that people are recognised, empowered, and overall treated equitably by their managers and peers.
"In fact, things have gotten worse."
It went on to say: "Racism, discrimination, bias, and aggression do not come from the big moments. It's in the small actions that mount up over time and build into a culture where we are only meant to be seen as quotas, but never heard, never acknowledged, never recognised, and never accepted."
The memo was accompanied screenshots from an app allowing Facebook employees to anonymously speak of their experiences, with one user reportedly saying: “These people make it seem like they work for the KKK.”
Facebook released a statement on Friday, in which Bertie Thomson, vice-president of corporate communications, apologised for the complaints in the letter.
Mr Thomson said: "No one at Facebook, or anywhere, should have to put up with this behaviour. We are sorry. It goes against everything that we stand for as a company. We’re listening and working hard to do better.”