A group that claimed to be able to “cure” homosexuals and turn them straight will be sued on Wednesday in a New Jersey courtroom for violating the state’s consumer protection act.

Opening arguments in the jury trial of Michael Ferguson et al versus Jonah will start at 9.30am on Wednesday in the superior court of New Jersey. Four men who took part in conversion therapy sessions and two of their parents will press the jury to award them damages on the never-before-tested grounds that the organizers were guilty of making false promises and misrepresentation.

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The lawsuit has been brought by the Southern Poverty Law Center, which monitors hate groups and extremists, as a landmark attempt to tackle conversion therapy through consumer rights legislation. According to the legal complaint, the leaders of Jonah made a number of false and discredited claims that amount to fraud.

Jonah, previously known as Jews Offering New Alternatives for Homosexuality, presented gay orientation as a matter of choice and “learned behavior”. The group described its therapy, which could cost as much as $10,000, as “scientifically based”. Its literature cited in the complaint said that “anyone can choose to disengage from their same-sex sexual fantasies, arousals, behavior and identity”.

An article posted on the Jonah website called “How do I walk away from homosexuality” said that through “introspection and healing past wounds, we heal the underlying causes of our same-sex attraction. In most instances, people who do this feel the force of the same-sex attractions diminish, and heterosexual attractions grow.”

Conversion therapy, also known as reparative, reorientation or ex-gay therapy, has been widely dismissed over many years by professional bodies such as the American Psychiatric Association and American Psychological Association. A growing number of states have also moved towards banning conversion therapy as potentially damaging to those subjected to it, particularly the young.

New Jersey, where Jonah was based, has implemented a ban, as have California and Washington DC. In April the White House added its name to the call for a ban.

Jonah was set up in Jersey City by a former Wall Street executive, Arthur Goldberg. He is named as a defendant in the case, as is Alan Downing, who acted as the company’s “life coach”.

In a motion to dismiss the case brought in 2013, the defendants argued that the nature of sexual orientation was still a matter of considerable debate in scientific circles. “Debate rages in the scientific community – and in society generally – over the immutability of sexual orientation and the efficacy and safety of SOCE [sexual orientation change efforts].”

The motion accused the plaintiffs in the case of trying to “shut down the debate by making one viewpoint on the issue literally illegal”.

The four former clients of Jonah allege in their complaint that the organizers of the therapy engaged in several unorthodox therapeutic techniques, such as instructing participants to remove all their clothing in group sessions and telling them to beat an effigy of their mothers with a tennis racket. Clients were allegedly subjected to ridicule by being called “faggots” and “homos” in mock gym classes. “You’re such a fag, homo, queer boy,” clients were told in a different session.

One of the plaintiffs, who is likely to give evidence, alleged in the legal complaint that he was told to wear a rubber band around his wrist and snap himself whenever he felt attracted to another man.

The trial is expected to last several weeks.