Advocates of a “medicine” called MMS will gather in a hotel in upstate New York on Saturday to promote what they claim to be a miracle cure for cancer that is in fact a powerful bleach that can cause serious harm and even death.

The self-proclaimed “Genesis II Church of Health and Healing” – a group that in reality is neither a church nor a medical outfit – plans to lure supporters and unsuspecting individuals to a “seminar” at the Marienthal Country Inn in Eden, New York. It is charging $450 per person, or $800 for a couple, for the privilege of being inculcated over two days into the false promises of its remedy, “miracle mineral solution” or MMS.

A document seen by the Guardian shows that the group intends to provide the industrial-strength bleach to attendants for them to drink. “We just might surprise everyone every so often with a dose of MMS1. Be ready,” its literature states.

Earlier this week it posted on its Facebook page a video of a man firing multiple handgun rounds in a shooting range above the caption “More G2 Church security training”.

The New York meeting comes just five days after the US Food and Drug Administration put out its strongest warning about MMS. It bluntly warned consumers not to buy or drink the product which it called a “dangerous bleach which has caused serious and potentially life-threatening side effects”.

The acting commissioner of the FDA, Ned Sharpless, said that “miracle mineral solution and similar products are not FDA-approved, and ingesting these products is the same as drinking bleach. Consumers should not use these products, and parents should not give these products to their children for any reason.”

The ‘sacramental kit’ sold by Genesis II Church of Health and Healing is referred to as MMS, or ‘miracle mineral solution or supplement’. Photograph: https://g2sacraments.org/G2-Sacramental-Kit-p46564880

The FDA has pledged to track down the peddlers of the bleach and “take appropriate enforcement actions against those who attempt to evade FDA regulations and market unapproved and potentially dangerous products to the American public”. So far though there is no sign of the agency taking action against the Genesis II meeting on Saturday, despite complaints having been made to federal officials by health campaigners.

Dealers in MMS usually sell the product in two parts: sodium chlorite and citric acid. The two liquids are combined to make chlorine dioxide, a powerful bleaching agent used in industrial processes including textile manufacture.

Genesis II sells the liquid online for $20 for a four-ounce bottle. It tries to evade federal regulations by cloaking the product in pseudo-religious language – payments are “donations” and the bottles of bleach are “sacraments”.

The peddlers claim that drinking the bleach can cure any number of serious illnesses, including cancer, HIV/Aids and malaria as well as autism. The FDA however points out that there is no scientific evidence supporting either the safety or effectiveness of the product – on the contrary, when imbibed it can cause severe vomiting, diarrhea and potentially fatal low blood pressure arising from dehydration.

The operation is masterminded by Mark and Jonathan Grenon, who have given themselves the title of “bishops” within the “church”. A video posted by Jonathan Grenon on Facebook last September shows the production of the substance in a shed in Florida that is being used as a makeshift factory.

The Grenons, acting as yet with impunity, have begun touting their dangerous formula globally. Recent “seminars” similar to this weekend’s event in New York state have been held in Chile, Ecuador, South Africa and New Zealand.

Genesis II was cited as an influence behind a massive distribution of the bleach to up to 50,000 poor villagers in Uganda. The network, exposed by the Guardian, was set up by an American pastor with the support of a British man, Sam Little, who has now been charged by Ugandan authorities with carrying out illegal clinical trials involving impure drugs.

Fiona O’Leary, a campaigner against pseudo science whose work helped to get MMS banned in Ireland in 2016, said that the New York seminar posed a threat to vulnerable people. She called on the FDA to shut it down.

“The Grenons plan to dose their ‘students’ with this toxic bleach and will be mixing these dangerous chemicals at this seminar. The FDA know all about the Grenons for many years but have ignored our many complaints to date,” she said.

The Guardian asked Mark Grenon why he was peddling a potentially dangerous chemical to residents of New York state under the pretext that it was a miracle cure. He replied by email that “you and your Guardian newspaper are just puppets of the evil players of this world like the Murdoch/Rothschild families!”