A British man and his daughter who were severely injured in a 2017 suicide bombing at a concert in England won a harassment lawsuit on Wednesday against a conspiracy theorist who had claimed that the terrorist attack was an elaborate hoax.

The British case echoed the U.S. lawsuit against a conspiracy broadcaster, Alex Jones, that was brought by the families of the victims of the mass shooting at the Sandy Hook Elementary School in 2012. Mr. Jones was convicted of defaming the victims’ families and ordered to pay $1.5 billion.

A judge in a civil court in England ruled that Richard D. Hall had harassed the Hibbert family in his creation of a false narrative, in which Mr. Hall claimed in a book and video that the bombing at Manchester Arena was a “well-planned fake terrorist incident,” in which the victims were “crisis actors,” court documents said.

“I have no doubt that his course of conduct was a negligent, indeed reckless, abuse of media freedom,” Justice Karen Steyn wrote, according to a court statement.

A separate hearing will be set to determine damages.

The attack by Salman Abedi, a 22-year-old suicide bomber, at the arena where the U.S. pop singer Ariana Grande was performing killed 22 people and permanently injured dozens more.

Martin Hibbert and his daughter, Eve Hibbert, were among the victims: He was paralyzed from the waist down, while his daughter suffered severe brain damage. Mr. Hall spent years trying to prove that the two were not even at the concert, court documents showed.

“We shouldn’t have to face such allegations that the Manchester Arena attack never happened, and that our injuries were not as a result of the bombing,” Mr. Hibbert, who suffered 22 shrapnel wounds, said in a statement after the ruling. His daughter, who was 14 at the time of the attack, now needs full-time care, his lawyers said.

In 2020, Mr. Hall published a video and book, both titled “Manchester: The Night of the Bang.”

In collecting his purported evidence, Mr. Hall secretly recorded footage of Eve Hibbert at home, knocking on the family’s front door and interviewing neighbors, the court heard.

Mr. Hall denied the family’s claims, arguing that he had the right to publish his opinions. An engineer by profession, Mr. Hall turned to publishing in 2009 after starting a website design company.

The ruling sent “a very clear message to people who think they have the right to publish absurd, harmful, unfounded allegations against others,” Kerry Gillespie, the family’s lawyer, said in a statement.