A well-known activist who played a significant role assisting Black Lives Matter activists and other demonstrators in Ferguson and Baltimore was arrested last month in Prince George’s County and charged with prostitution and human trafficking.

Police accuse Charles Wade — founder of Operation Help or Hush — of using online ads to organize meetings between a 17-year-old girl and Johns who paid her for sex, according to court documents.

Wade was arrested, the documents state, on suspicion of setting up a meeting April 25 at a Howard Johnson Inn in College Park, where the teenager agreed to have sex with an undercover detective during a sting operation.

The police report, provided to The Post by the Prince George’s County state’s attorney office, alleges that Wade was “watching” the undercover officer as he entered the hotel room in which the prostitution was scheduled to take place.

In a subsequent interview with police, the documents state, the woman said Wade was aware of her age and referred to himself as her “manager.”

“You only have five months until you’re 18 so I’m not worried,” he is accused of telling her, according to the documents.

Wade — whose trial is scheduled to begin June 3 — faces multiple counts of prostitution and human trafficking, the documents state.

The 33-year-old posted $25,000 bail two days after his arrest, which was first reported by the St. Louis Post-Dispatch.

Wade has vehemently denied the charges. In a statement posted on Twitter, he said he had been providing temporary housing for the teenager, who had apparently told him she was 20. He said his organization handles large numbers of temporary-housing requests for people in need and that he had treated the young woman’s situation accordingly, using hotel rewards points he had amassed over the years.

“As the person who booked, paid for, checked in with government issued identification, I was also arrested as I was walking to a store on about a half dozen charges related to her activities and arrest,” the statement said.

Wade told The Washington Post on Monday that his work has always been humanitarian in nature and that his arrest was part of a larger effort to link him to — and discredit — Black Lives Matter, a movement he claims he has been associated with but never involved with politically.

“This case is highly politicized for obvious reasons; but I also feel like there are parts of this that are clearly sensationalism and there are parts of this that are doing anything possible to discredit a larger movement, which I have been associated with,” he said. “The claims are obviously so absurd that they border on satire for me, but they are not funny because they have real-life consequences.”

Those consequences, Wade said, have come in the form of online threats to his family, which, he said, has been threatened with lynching and other forms of violence.

“First and foremost,” Wade said, “this is a legal matter, and my freedom is not predicated on the court of public opinion. I’m confident that I will be exonerated.”

A Post report about Ferguson activists last year noted that Wade, a native of Bowie, Md., once worked as an image consultant for Solange Knowles, sister of pop star Beyoncé. After Michael Brown’s shooting death at the hands of a white police officer sparked unrest in Ferguson, Mo., Wade began raising money on Twitter to help protesters with basic needs, including food, housing and gas.

Wade eventually started Operation Help or Hush to formally assist the protest movement.

“Effective community organizing requires infrastructure and supplies to endure,” the organization’s online description says. “We buy supplies for making signs, cover travel expenses, ensure organizers have food and shelter, and develop systems to link organizers together.”

When The Post caught up with Wade in 2015, he said he was extremely busy juggling challenges large and small.

“It’s really demoralizing that you have to fight so hard just to do something decent for people,” he said then.

On Monday, Wade struck a similar tone while discussing his arrest, telling The Post that his efforts to help people had backfired — but that, ultimately, he held himself responsible for not being more diligent in vetting the teenager’s background.

“For that reason alone, I’ve paused any further work,” he said. “My primary focus is my safety, my sanity, peace, and addressing the legal matter that is at hand.”