Understaffing at the Cannabis Control Commission is to blame for delays in processing medical marijuana patient cards, according to the union representing the workers who process those applications.

“There’s just not enough staff, and people are stretched really thin,” said Megan Piccirillo, a spokeswoman for SEIU Local 509.

Cannabis Control Commission Chairman Steven Hoffman disagreed that the problem is solely staffing. Hoffman said the issue is an ongoing one, which the commission is trying to fix, working collaboratively with the union. “I don’t think it’s a new issue,” Hoffman said. “It’s just one that has not yet been fixed, and we’re committed to fixing it.”

Medical marijuana patients have been complaining that the Cannabis Control Commission, which took over the medical marijuana program from the Department of Public Health in December, has been taking weeks or even months to approve applications for patient cards. Long wait times had been an issue previously at the Department of Public Health, but patient advocates said the wait times had improved before the commission took over.

SEIU represents a small number of commission employees, formerly DPH employees, who process applications for medical marijuana cards.

Jennifer Doe, an internal organizer for SEIU Local 509 who works with those employees, said at its high point, the union represented eight people who processed medical marijuana applications. Now, there are four workers in those roles, one of whom is out on leave.

Doe said some workers left because the Cannabis Control Commission would not tell them whether they would remain in Boston or move to the commission’s new headquarters in Worcester. She said the Department of Public Health held off on hiring because of the transfer to the commission, and the commission “shows no intention to hire.”

Doe said the office is a “stressful environment” where people have “more work than they can handle.”

According to a complaint the union filed with the Department of Labor Relations, the commission and SEIU talked about workload issues in April, and the commission proposed hiring nonunion temporary workers to do work that had been done by union members.

The complaint says before the sides were able to reach an agreement about temporary workers, the commission in mid-May hired a temporary worker to process applications and work on the state’s “virtual gateway” medical marijuana database. The union says the commission violated state law by hiring a nonunion worker before the completion of union bargaining.

Doe said temporary workers do not have the same wages, benefits or training. “As a result, you have a massive backlog in the processing of people’s applications and renewals,” she said.

Hoffman declined to comment on the complaint about hiring nonunion temporary workers, referring questions to the state agency that oversees union negotiations. “We have a collaborative relationship with the union, and we’re all trying to accomplish the same objectives, which is to serve the patients of the state as well as we possibly can,” Hoffman said.

(Human Resources Department General Counsel Michele Heffernan said the department is unable to comment on pending litigation.)

But Hoffman said the commission is trying to improve the medical marijuana process by bringing the medical licensing program into the same portal that handles recreational licenses and by improving the “gateway,” which is the medical marijuana computer system.

“There’s a number of actions that are going on to try to make us more responsive to patient needs, and I recognize that we have more work to do,” Hoffman said.

Asked if that included adding staff, Hoffman said the Cannabis Control Commission overall has 61 or 62 staff, and its staffing plan calls for having 72 or 73 by now. “We’ve always intended to add more staff, and we are adding more staff,” he said.

Hoffman said the agency is currently hiring licensing agents and compliance officers. He would not specify whether it is hiring specifically for the medical program.

“We know we have more staffing to do, and we’re doing it,” Hoffman said. “It’s just one of the many things we’re doing simultaneously. We always said we are developing regulations and giving out licenses while we’re building an agency.”

In the meantime, patients say they are waiting for medicine.

Mike Crawford, a medical marijuana patient and longtime legalization advocate who has been vocal in raising concerns about the delays, said, “To me, this is definitely a staffing issue.” He said he is hearing from patients who have to wait three months to get a patient card approved.

Nichole Snow, executive director of the Massachusetts Patient Advocacy Alliance, said she spoke to the commission soon after the transfer when patients were having trouble reaching the program by phone and getting registrations renewed. “To the patients, it was a change in quality of service,” Snow said.

The commission plans to start a new program July 1 that will let new medical marijuana patients buy an initial 14-day supply of marijuana before their registration card comes in the mail. That will not apply to renewals.

Asked whether he could commit to getting patient wait times down, Hoffman said, “I am committed to make this work. So yes, we will make it more responsive, we will shrink the wait times, and we will keep working as hard as we can in collaboration with the union until we do that.”

This story was updated with Heffernan’s response.