Essure is a tiny coil that's implanted into the fallopian tubes, with no incision. Scar tissue forms around the coils, permanently closing off the fallopian tubes.
It was designed and manufactured by the Mountain View-based company called Conceptus, which is now owned by Bayer.
But some women have complained of abdominal pain, bleeding, and bloating.
Brockovich has launched a campaign to have Essure taken off the market.
"There's something wrong with the device, in my opinion," Brockovich told ABCNews.com. "It's a form of permanent birth control, and women's organs are being perforated … It's ridiculous that at any level we try to defend this. If 30 women did suffer harm for unknown reason, we'd investigate. We have thousands injured. I don't think it's safe."
Brockovich said she has no financial stake in the outcome of this campaign.
Bayer says Essure was approved by the FDA and is well-documented to be safe and effective.