Democratic Gov. Gavin Newsom of California took a moment in his keynote speech at the Vatican's Climate Summit last week to jab Donald Trump, accusing the former president of cozying up with big oil companies in what he called "open corruption."

"And with respect and, forgive me, if this comes off a little too harsh. It’s been said and I’ll repeat it: the polluted heart of the climate crisis are these fossil fuel companies that have been lying to us," Newsom said in his 10-minute speech Thursday. "They’ve been deceiving us. They’ve known the science. They’ve denied the science. They’ve delayed advancement."

"And in peril of further alienating some, I have to call this out as well. I don’t want to talk in the paradigm of a political conscience – I mentioned two Republicans, but let me mention one other," Newsom continued. "Former President Donald Trump, who just last week, I never thought I’d see this. I’ve heard it, but I’ve never seen it. Donald Trump, just last week, had oil executives convening, talking about his election. And he openly asked them for $1 billion to roll back the environmental progress of the Biden administration, the environmental progress that we’ve made over the course of the last half century. Open corruption."

NEWSOM IGNORING CALIFORNIA CRISES TO PROMOTE HIMSELF IN PRO-ABORTION CAMPAIGN, GOP LAWMAKERS SAY

Newsom's reference was to a meeting the former president reportedly had at Mar-a-Lago with top oil excecutives, the New York Times reported earlier this month, citing two people who were present at the meeting. 

The Vatican summit, which was spearheaded by Pope Francis in 2022 after he deemed climate change an "ecological sin" caused by human negligence, is organized by the Pontifical Academy of Sciences. According to the academy, so-called climate resilience "requires both cross-disciplinary partnerships among researchers, engineers, and entrepreneurs, as well as [transdisciplinary] partnerships between science and community leaders including faith leaders, NGOs, and the public."

"Mayors and Governors form the core of such transdisciplinary partnerships," it says on its website.

During Newsom's speech, he also hailed California as a leading example in its progressive green energy policies, as the state is investing more than $48 billion in climate change initiatives alone, including $10 billion in zero-emission vehicles and chargers.

"California has exceeded its nation-leading environmental goals," Newsom said. "We’re in the ‘how’ business, and it’s about the power of emulation, proving that we can run the fifth-largest economy, its economic engine, as we change the way we produce and consume energy."

However, the Golden State will fail to meet its climate change mandates unless it nearly triples its rate of reduction of greenhouse gases through 2030, an analysis in March by Beacon Economics, an L.A.-based economic research firm, reported. Newsom's office dismissed the report at the time to Fox News Digital and said "we'll continue proving everybody wrong."

OUTSPOKEN PRO-ABORTION GOVERNOR GETS SPEAKING SLOT AT VATICAN SUMMIT

Nonetheless, Newsom's invitation to speak at a prominent Vatican event came as a surprise to many. Newsom, who is Catholic, has touted social progressive policies – often at odds with the Catholic Church's dogma – in his state since he assumed office in 2019. 

One of those policies was when the blue-state leader made California the first "sanctuary state" in 2022 for transgender children from more restrictive states seeking sex-change surgeries. Meanwhile, the Vatican also formally reaffirmed and expanded on the Catholic Church's teaching regarding gender theory – which it holds as an inadmissible ideology – asserting that attempts to alter an individual's immutable gender are ultimately misguided attempts to play God.

But in an interview that aired Sunday, Pope Francis took aim at conservatives opposed to the evolutionary doctrines of the Catholic Church, saying they held a "suicidal attitude" toward it. 

VATICAN PREPARING DOCUMENT ON 'IMMORAL TENDENCIES': GENDER THEORY, SURROGACY, AND MORE

Francis was asked about his controversial comments about LGBTQ individuals and the Vatican's endorsement of blessings for individuals in same-sex relationships during the "60 Minutes" interview that aired on Sunday. Host Norah O'Donnell asked him if he had a message for conservative bishops in the U.S. who've criticized his "efforts to revisit teachings and traditions" in the church.

"You used an adjective, 'conservative.' That is, conservative is one who clings to something and does not want to see beyond that," Francis said. "It is a suicidal attitude. Because one thing is to take tradition into account, to consider situations from the past, but quite another is to be closed up inside a dogmatic box."

Fox News Digital's Kristine Parks contributed to this report.