It's the latest in a series of public stands made by Google employees or contractors against aspects of the company culture. A coordinated walkout by employees around the globe protesting discrimination and sexual harassment at Google led the company to end forced arbitration for claims. Last month, several hundred employees signed onto a letter protesting the company's censored search efforts in China.
A Bloomberg report in July said Google parent Alphabet had more contractors than direct employees this year, for the first time ever.
"Google's mission is to 'organize the world's information and make it universally accessible.' But the company fails to meet this standard within its own workplace. Google routinely denies [temporary, vendor, and contract workers] access to information that is relevant to our jobs and our lives," the letter published Wednesday says.
The latest letter is signed only by "TVCs at Google" and does not indicate the number of people backing the effort.
The letter also says TVCs at YouTube, which is owned by Google, were not provided with security updates when an active shooter entered the company's headquarters in April. Only full-time employees received the updates.
"When the tragic shooting occurred at YouTube in April of this year, the company sent real-time security updates to full-time employees only, leaving TVCs defenseless in the line of fire," the letter says. "The exclusion of TVCs from important communications and fair treatment is part of a system of institutional racism, sexism, and discrimination. TVCs are disproportionately people from marginalized groups who are treated as less deserving of compensation, opportunities, workplace protections and respect."
A Google spokesperson said in a statement to CNBC that the company worked during the shooting to provide parallel updates for full-time employees and TVCs. In some cases those updates were sent via through the TVC's employer, the spokesperson said.
TVCs were invited that week to the company-wide town hall discussion at YouTube that is usually reserved for full-time employers, the spokesperson said. The TVCs who wrote the letter said they were not invited to "a town hall discussion," but it's not clear which discussion they were referencing.
The letter demands, among other things, better compensation for TVCs and access to staff town hall discussions.
In October, a Google spokesperson told CNBC, "At the end of the day, TVC (temporary, vendor and contractual workers) are an important part of the workforce, but they are not Google employees and not privy to the same confidential company information that full-time Googlers are."
Read the full letter on Medium.
—CNBC's Ellen Sheng contributed to this report.