Nxivm boss Keith Raniere has already been exposed as a cult leader and convicted of fraud and sex trafficking. Now a new TV special alleges he might have had a role in four mysterious deaths.

In “The Lost Women of NXIVM,” airing Sunday on Investigation Discovery, former cult insider Frank Parlato alleges Raniere may have been involved in the deaths of at least four women who were close to the organization.

Kristin Snyder, Barbara Jeske, Gina Hutchinson and Pamela Cafritz died under what Parlato and others say are suspicious circumstances. The deaths span a 14-year period between 2002 until 2016. The women had been intimately involved with the Nxivm leader.

“I don’t think the official stories on the deaths of these four women should be allowed to rest without a challenge,” Parlato told The Post.

The show includes video of Raniere secretly recorded by a then-follower. “Here’s the thing,” he warns on the tape. “I’ve had people killed because of my beliefs — or because of their beliefs.”

“Keith didn’t kill anyone,” said Raniere lawyer Marc Agnifilo. “That is an insult to real forensic investigation as well as to the people who have passed away.”

Once a powerful “self-help” organization whose supporters included the billionaire Bronfman family, Nxivm was exposed by Parlato — who worked for the group as a publicist in 2007 — and others as a violent sex cult. Raniere was convicted on federal charges including sex trafficking and possession of child pornography. He is to be sentenced next year.

Although Snyder’s and Hutchinson’s deaths were ruled suicides — by drowning and gunshot, respectively — Parlato believes there may be more to it. In the months before they died, the women had become irritating for the guru.

“Gina Hutchinson [age 33 when she died] was going around saying she had sex with Raniere when she was 14 years old. Others, including her sister, have verified this,” Parlato said of the New York woman.

Snyder, meanwhile, had begun telling a Nxivm class in Anchorage, Alaska, that she was pregnant with Raniere’s child. She was ejected from a seminar and disappeared less than 24 hours later. A suicide note was later found in her truck.

Around the time of their deaths, Raniere had been passing himself off as celibate, and the women’s stories posed an existential threat to his nascent movement.

The deaths of Jeske and Cafritz, meanwhile, were attributed to cancer that developed after both women lived with Raniere in his Halfmoon, NY, home. Jeske died in 2014 at 63, Cafritz in 2016 at 57.

But Parlato has suspicions about those deaths as well.

Tests on another woman who spent time in the home and subsequently developed cancer revealed unusually elevated levels of ­bismuth and barium.

Parlato believes they all had been ­poisoned.

“Keith was handling their treatment. He was managing their diet. He was controlling the refrigerator,” Parlato alleged.

Jason Kolowski, a forensic consultant interviewed for the documentary, said hair samples from the women revealed a “chronic ­exposure” to the heavy metals — and speculated that it may have come from rat poison.

“Keith was handling their treatment. He was managing their diet. He was controlling the refrigerator. He had the women all on very low-calorie diets,” Parlato alleged. Jason Kolowski, a forensic consultant interviewed for the documentary, said he was confident hair samples from the women revealed a “chronic exposure” to the heavy metals — and speculated that it may have come from rat poison.

“Is it possible that Keith Raniere poisoned these women over a period of years?” Parlato asks in his documentary. “The secrecy surrounding him and his inner circle makes anything possible.”