An anti-sex abuse activist — who was a daily fixture at the trial of convicted child molester Nechemya Weberman — had bleach splashed in his face yesterday on a Brooklyn street.

Crusading Rabbi Nuchem Rosenberg, 62, was ambushed as he walked down Roebling Street across from Schnitzler’s Famous Fish market around noon, he and witnesses told The Post.

“He comes up to me and he taps me on the shoulder,” the still-shaken Rosenberg recounted after being treated for ocular burns at Woodhull Medical Center.

“He walked up hard to me. He looks me in the face. I saw him holding a glass. I thought it was coffee or something and he throws it in my face.”

Rosenberg runs an information hot line and blog for sex-abuse victims and was a regular at the just-ended trial of powerful Hasidic leader Weberman.

He claims the attack was in retaliation for his staunch support of Weberman’s now 18-year-old victim.

On Monday — as Weberman was convicted Monday on 59 counts of abusing of a Brooklyn schoolgirl — Rosenberg posted on his blog accusing another rabbi of abusing young boys.

The activist also posted on Twitter after Weberman’s conviction.

“Burech hashem!! (Praise God!!),” he tweeted. “Chazer (Pig) Weberman Is Arrested After All 60 Charges Was Totally True! Rabunim & Chazerim (Rabbis & Pigs) Are All The Same Garbage.”

“Two days later, this is what happens,” Rosenberg said.

Police had not charged anyone late yesterday in the alleged assault, though identified a suspect they planned to question.

Witnesses said the bleach-tossing thug fled the street after dousing Rosenberg.

Primo Santiago, who manages a liquor store on the same block as the fish market, said, “It happened so fast. Out of the corner of my eye I saw [Rosenberg] walking down the street, and the other guy ran from the fish store and threw the bleach.

“He didn’t say anything.”