California voters are likely to put the kibosh on the state’s controversial proposed “Billionaire Tax,” according to a poll exclusively obtained by The Post.

The survey conducted by David Binder Research found that the proposed wealth-tax ballot measure initially had a slim majority of support, with 55% of voters saying they liked the idea of the one-time 5% tax on California residents worth more than $1 billion.

But support has since collapsed to just 41% of voters, while those opposed surged to 53% — after respondents heard arguments from both sides, the pollsters said.

“A majority of voters feel the wealth tax will be ineffective and not make a difference in the gap between the extremely wealthy and everyone else,” pollsters write in their report.

“While 53% say the measure won’t make a difference in the gap between the extremely wealthy and everyone else, only 32% say the measure provides an opportunity to reduce the gap.”

The poll surveyed 800 likely California voters from Dec. 6-10. It was conducted in both English and Spanish and had a margin of error of 3.5%.

Gov. Gavin Newsom has steadfastly opposed the billionaires tax.

Izzy Gardon, a rep for the governor’s office, said Newsom believes that a state-only level wealth tax would “drive a race to the bottom.”

In a prior interview, Newsom said: “You can’t isolate yourself from the 49 [other states]. We’re in a competitive environment.”

Dan Newman, a political consultant, told The Post on Monday that the proposal — pushed by labor unions to help cover federal budget cuts funding such services as health care — “is terribly drafted, unworkable, illegal and would have hugely negative consequences to the state’s economy.

“It’s gambling a potential one-time revenue bump in exchange for massive ongoing losses, which would force cuts to schools and healthcare, and leave regular taxpayers on the hook to make up the difference,” Newman said.

Suzanne Jimenez, chief of staff for SEIU-United Healthcare Workers West, which is leading the proposed ballot measure that could raise up to $100 billion to help cover federal cuts to health care, slammed the people behind the poll as “political insiders.”

“Californians don’t have time for games when $100 billion in federal healthcare cuts threaten to close hospitals and emergency rooms and create chaos across our healthcare system,” Jimenez said in a statement.

“What’s clear is that some political insiders are comfortable playing politics with people’s health,” she added. “The poll cited in this story was funded by opponents of the Billionaire Tax who are more interested in sowing doubt than in offering real solutions to the healthcare cuts Californians are facing.”

Chamath Palihapitiya, a venture capitalist and entrepreneur who co-hosts the Alll In podcast, blasted out a tweet Saturday claiming California has lost $1 trillion in wealth in the past month alone as billionaires have fled the state to shield their assets.

“We had $2T of billionaire wealth just a few weeks ago,” Palihapitiya wrote on X.

“Now, 50% of that wealth has left — taking their income tax revenue, sales tax revenue, real estate tax revenue and all their staffs (and their salaries and income taxes) with them.”