The shutdown of the adult classifieds section on Backpage.com will endanger the lives of sex workers and make it harder for officials to investigate trafficking and support victims, civil rights advocates said.

Backpage, a popular Craigslist-style website where workers have long advertised a range of services, announced on Monday that “unconstitutional government censorship” has forced the company to remove its adult content. The closure comes after prosecutors across the US have aggressively targeted the site and its executives, claiming that Backpage facilitates and profits from pimping and human trafficking.

But sex workers have long argued that Backpage provides a safe public platform to vet clients and report predators, and that without it, the industry will be pushed further underground. On Tuesday, activists said the termination had removed a source of income for many vulnerable people and would force some with no choice but to work on the streets where they are much more likely to face violence and police harassment.

“A lot of lives are being destroyed,” said Kristen DiAngelo, executive director of the Sex Workers Outreach Project of Sacramento. “These are human and civil rights abuses. How many sex workers across the US now have no way to support themselves?”

Newly elected US senator Kamala Harris led the fight against Backpage as California’s attorney general, repeatedly filing charges against the site’s operators, claiming the platform was an “online brothel”. But judges across the country have continually sided with the website and first amendment advocates, citing a law that is foundational to free speech on the internet, which dictates that platforms are not liable for the postings of users.

Despite the legal victories, including the supreme court’s decision on Monday not to hear an appeal against Backpage, the US Senate has intensified scrutiny of the company with a report and hearing on Tuesday, leading the site to replace its adult section with a banner that reads “CENSORED”.

Targeting Backpage, activists say, is part of a broader campaign by liberal and conservative lawmakers in America to further criminalize sex work, which research has shown does little to protect victims of trafficking while making it harder for consenting adult workers to safely do their job.

Targeting Backpage, activists say, is part of a broader campaign by liberal and conservative lawmakers in America to further criminalize sex work. Photograph: Justin Tallis/AFP/Getty Images

“It’s really a sad day,” said Lois Lee, founder and president of Children of the Night, a national hotline and shelter program for sex trafficking victims.

Lee’s organization had advertised its services on Backpage, and she said she helped build partnerships between the company and police so that law enforcement could use the platform to investigate trafficking.

“It was a useful tool,” she said. “That’s gone now.”

Shuttering Backpage does not stop pimping, but it does make it harder for authorities and for sex workers to detect that kind of dangerous activity, said Maxine Doogan, president of the Erotic Service Provider Legal, Educational and Research Project.

“There’s no research that says removing advertising sites reduces trafficking,” said Doogan, noting that women used the site to carefully screen clients, who could provide references to other Backpage workers. “Everybody is scrambling.”

People are panicked … They’re saying if they can’t make money on Backpage today they have to be on the streets tonight Kimberlee Cline, sex worker who used Backpage

“People are panicked. They’re thinking about paying bills and buying food,” said Kimberlee Cline, a Sacramento-based sex worker who used Backpage. “They’re saying if they can’t make money on Backpage today, they have to go and be on the streets tonight.

“On the streets,” she added, “there’s no screening at all. It’s just based on gut.”

The ongoing political campaign to force Backpage to close is another example of how US lawmakers ignore sex workers in policy debates on trafficking, said Ellyn Bell, a former nonprofit director who has written about child exploitation.

“Sex workers’ voices need to be taken into consideration,” she said, adding, “It really comes down to decriminalization. There has to be a platform where people feel safe.”

In recent years, the shuttering of other adult services sites has left workers with very few options. In some communities, a loss of online ad platforms has directly led to reports of increased arrests of sex workers and sexual assaults on the job.

Since the Backpage news this week, DiAngelo said sex workers are already getting threats from pimps who are telling women they will now need to rely on them to get work.

“We’re going to see so many more people trafficked and pimped. Violence is going to escalate,” she said, in tears. “The bottom line is we’re going to see bloodshed.”