A new campaign chaired by a Massachusetts General Hospital surgeon will oppose a potential ballot question seeking to decriminalize some psychedelic substances.

After coming together “reasonably quickly” in the past week, as spokesperson Chris Keohan put it, organizers filed paperwork with state campaign finance regulators making their plans official to fight against the measure that could boost access to substances such as psilocybin from mushrooms and mescaline, both at licensed facilities and at home.

Keohan, a partner at Shawmut Strategies Group, said the Coalition for Safe Communities opposes the initiative petition because it would allow Massachusetts adults to grow certain psychedelic substances in a 12-foot-by-12-foot area at home.

“We’re not arguing against the therapeutic value,” Keohan told the News Service. “We see real danger in the ability to grow at home, especially the square footage it allows. This allows for 144 square feet of home growth, which is the equivalent of the average bedroom in Massachusetts.”

Anahita Dua, a surgeon who directs the vascular lab at MGH, chairs the new OCPF committee. Keohan said she voiced “significant opposition” and offered her help to organize other medical and mental health professionals against the measure.

Some psychiatric experts, including leaders of the Massachusetts Psychiatric Society, previously raised warnings to lawmakers about their own concerns with the proposal.

Opponents also plan to try and sway law enforcement leaders and prosecutors to their side. Keohan said the campaign has reached out to several district attorneys, describing them as “very interested in what the coalition will be saying.”

The Foundation for Drug Policy Solutions and Smart Approaches to Marijuana groups are on board with the opposition campaign, according to Keohan.

“Since the measure allows individuals to give out the psychedelics they grow at home to others, it creates a massive loophole that will open the door to an unregulated and unsafe black market,” Keohan said.

Jennifer Manley, a spokesperson for the campaign supporting the question, called it “reckless and irresponsible to disregard top medical research institutions studying and working with psychedelics.”

“Now isn’t the time to limit mental health options in Massachusetts,” she said. “We owe it to people that are suffering from PTSD, anxiety, depression and other treatment resistant issues to give them another option that may really help them.”

The proposed ballot question would clear the way for legal psychedelic use in Massachusetts. It calls for no legal action against adults ages 21 and older for “possessing, using, processing, or testing not more than a personal use amount of a natural psychedelic substance,” and allows home growth of the plants or fungi cultivated for psychedelic substances as long as they are in an area secured from minors.

Adults could possess up to one gram of psilocybin, one gram of psilocyn, one gram of dimethyltryptamine, 18 grams of mescaline and 30 grams of ibogaine on their person at one time under the proposal, and they could also give away that amount to another adult so long as they do not charge for it or promote it publicly.

If someone grows enough of the relevant plants or fungi to surpass the possession limit, everything in excess must remain at the residence where it was cultivated, according to the proposal.

Use of psychedelic substances would be prohibited in public spaces, and property owners, employers or government buildings and facilities can add their own restrictions as well.

The measure also envisions a system of licensed locations, where Bay Staters could go for treatments involving psychedelic substances under trained, professional supervision.

It calls for creation of a new Natural Psychedelic Substances Commission, whose members would be appointed by the governor, attorney general and treasurer, to create a regulatory framework for licensing, security and other related details.

The proposal does not allow for retail sales like those available in the recreational marijuana industry.

Supporters say the use of psychedelics, such as those found in “magic mushrooms,”can carry significant mental health benefits and help veterans, survivors of sexual abuse and others process trauma, recover from addiction and treat chronic pain.

New Approach, a Washington, D.C.-based political action committee, is leading the campaign here to boost access to psychedelics. Organizers previously managed similar successful ballot question campaigns in Oregon and Colorado.

Massachusetts for Mental Health Options, the group’s Massachusetts campaign finance committee, has raised nearly $4 million so far, most of it from more than a dozen six-figure or larger donations.

Filings with the state Office of Campaign and Political Finance list some noteworthy backers, as the Boston Globe reported in January. Toms Shoes Founder Blake Mycoskie, who last year pledged to give $100 million to psychedelics research, appears to have loaned the Massachusetts decriminalization campaign $500,000, according to OCPF records. Former “Buffy the Vampire Slayer” star Eliza Dushku Palandjian, who alongside her husband, Peter Palandjian, has funded addiction care at Brigham and Women’s Hospital, donated $100,000.

All One God Faith Inc., which produces Dr. Bronner’s soaps, gave the campaign $1 million, and Hubspot Chief Technology Officer Dharmesh Shah donated another $500,000.

A spokesperson for the pro-psychedelics campaign could not be reached for comment.

The opposition campaign has not reported any fundraising. Keohan said organizers are just now preparing to begin fundraising.

With the new anti-psychedelics coalition, all six topics that could reach the Nov. 5 ballot now have defined opponents who have either filed legal challenges alleging the measures are not eligible to go before voters or publicly criticized the proposals.

Lawmakers who reviewed all potential 2024 ballot questions recommended no legislative action to approve the psychedelics measure. In a report published Wednesday, a special committee said it understands “the importance of the potential for positive treatment,” but felt there was not enough evidence “that the widescale recreational legalization of these substances would be beneficial, let alone safe.”

“The Committee finds that the petition’s major goals – licensure and decriminalization – likely undercut each other by creating two separate systems for the use of psychedelic substances,” they wrote. “The petition would both create a system of state-licensed and taxed therapeutic facilities on the one hand and, on the other, decriminalize the cultivation, possession, and distribution of a variety of hallucinogenic and psychoactive substances. Voters are, therefore, being asked to simultaneously establish a potentially costly licensure system that imposes regulations on the cultivation methods, quality of product and allowable means of engaging certain users, while at the same time making the same substances widely available for individual cultivation and use across the Commonwealth in a non-licensed manner.”

Backers of the ballot question need to collect another 12,429 voter signatures and submit them to Secretary of State William Galvin’s office by July 3 to make the ballot.