(CNN) Former New York City Mayor Mike Bloomberg said at a private event in 2016 that his presidential campaign platform would have been to "defend the banks" and also labeled the progressive movement and Massachusetts Sen. Elizabeth Warren , now a rival for the 2020 Democratic presidential nomination, as "scary."

When asked his views on the rise of the far right in Europe, Bloomberg warned about the rise of progressive politicians in the US, citing Warren.

"The left is arising. The progressive movement is just as scary," he says. "Elizabeth Warren on one side. And whoever you want to pick on the Republicans on the right side?"

Bloomberg, who was elected mayor as a Republican and as an independent, also criticized President Barack Obama , saying that his 2012 endorsement of Obama was "backhanded" and that he thought Republican Mitt Romney could have done a better job if he'd been elected.

Bloomberg is now running a largely self-funded multi-million-dollar campaign for the Democratic nomination, positioning himself as a moderate as his rivals -- a crowded field that includes not just Warren but Vermont Sen. Bernie Sanders , a self-described democratic socialist who is now the front-runner -- are trying to paint him as an out-of-touch billionaire who is trying to buy an election. Bloomberg has argued that he is using his wealth to advance progressive causes and defeat President Donald Trump in November.

Audio of his comments, allegedly from a closed Goldman Sachs event for at Yankee Stadium on June 15, 2016, were anonymously sent to CNN by an email address called "CancelGoldman," with the author claiming he worked at Goldman Sachs for 14 years. The email called on Bloomberg to drop out of the race. The audio of the event, sent to CNN and a host of reporters was uploaded to audio hosting platform SoundCloud five days ago . Bloomberg's campaign confirmed the authenticity of the comments. CNN confirmed through Facebook photographs that Bloomberg took part in an event that day at Yankee Stadium. Goldman Sachs declined to comment, but did not dispute it was their event.

Stu Loeser, a spokesman for Bloomberg, said Bloomberg's comments about banks were a joke.

"The opening line was a joke," Loeser told CNN in an email. He added: "in the more serious parts of the speech, Mike tells very wealthy Americans that they need to break their addiction to cheap money that's exacerbating income inequality in America."

In the remarks, Bloomberg also spoke of the need for America to solve the problem of income equality before society "blows up."

"Well, to start, my first campaign platform would be to defend the banks, and you know how well that's gonna sell in this country," Bloomberg said in his remarks.

"But seriously," he went on, "somebody's gotta stand up and do what we need. A healthy banking system that's going to take risks because that's what creates the jobs for everybody. And nobody's willing to say that. The trouble is, these campaigns in this day and age, really are about slogans and not about issues anymore. And in this election you're going to see people are voting and they either love or hate, mostly hate both, but who you hate the least. That's what they're going to vote for. And they're not going to vote on issues."

Bloomberg added of the banking crowd, "these are my peeps."

He also said at the event that he had been prepared to run as an independent against both Trump and Hillary Clinton in 2016 and had lawyers in all 50 states to get him on the ballot, but as he's also said publicly, told the crowd that the best he could hope to get was a third of the electoral votes and said an independent had "no chance."

The head of privately held Bloomberg LP, a financial data and media company, said he didn't regret not running -- but joked that winning the presidency would have given him the benefit of using Predator drones on those who had "annoyed me or screwed me."

"It would have been a great job," says Bloomberg. "No, I mean, you think about it, you have Predators, and the Predators have missiles, and I have a list of everybody that's annoyed me or screwed me for the last 74 years, and bang-bang-bang-bang."

Bloomberg's spokesman acknowledged to CNN the joke on drones seemed inappropriate.

"Way back in 2016, when someone cracked wise about a President using military hardware to settle grudges, an audience would laugh," Loeser also wrote. "After three years of Donald Trump's daily drama, that might not seem so funny. What you hear in these remarks are a combination of jokes and detailed explanations of ways to make our government better that are far beyond what the current occupant of the Oval Office could read, let alone think."

Speaking about Obama, Bloomberg -- then still an independent -- described his 2012 endorsement as "back-handed" and said he did not think Obama did not do a good job in his first term, and that Romney would have done a better job if he could have governed as he did as governor of Massachusetts.

"The second Obama election I wrote a very backhanded endorsement of Obama," Bloomberg said. "Saying I thought he hadn't done the right thing, hadn't done, hadn't been good at things that I think are important and Romney would be a better person at doing that. But Romney did not stick with the values that he had when he was governor of Massachusetts."

Loeser, Bloomberg's spokesman, defended his comments on Obama.

"Regarding President Obama, he was making an important point," he told CNN in an email. "Everyone who read Mike's endorsement of President Obama saw that it was aimed at convincing Americans who saw merit in both candidates to vote for Obama. President Obama didn't need Mike Bloomberg to get out the vote from the strongest Obama voters. What Mike could and did do for President Obama is much like what he could and did do for Hillary Clinton when he spoke at the Democratic Convention in 2016 -- convince Americans who weren't already convinced of voting for the Democrat."

Former Vice President Joe Biden's campaign slammed Bloomberg's comments about Obama on Monday.

"Now we know that behind closed doors, Bloomberg described his last-minute endorsement of President Obama in 2012 as 'very backhanded' and said that he thought 'Romney would be a better person at doing' the 'things that I think are important.' Bloomberg may have changed his voter registration but he's still a Republican at heart," Andrew Bates, a Biden campaign spokesperson, said in a statement.

In his remarks, Bloomberg made historical reference to previous anti-elite revolutions.

"Look at the income inequality," he said. "Anytime we've had this before, society blows up and they do set up the guillotines and the guillotines don't have to be chop your head off. They could be confiscatory taxes, they could be seizing the endowments of uh, educational institutions and um, philanthropic organizations, all of which those proposals are out there. You know, you're going to have to do something about this income inequality and a lot of it comes from zero interest rates."

Elsewhere in the talk, Bloomberg suggested a New Deal-type solution to income inequality, saying "maybe the answer is another WPA because the corporate world's not going to do it there."

"The ways you get Congress to work for you is the ways you deal with your family," Bloomberg said. "You bribe them. You say to your kid, you say to your kid to 'clean your room or you don't get your allowance.' That's a bribe, I'm sorry."

Another speaker interrupted Bloomberg to suggest curfews, and Bloomberg agreed. "Curfews or you threaten them, 'If you don't do this no television,'" he said. "Or you try to reason with them you know, maybe you'll find $2 under your clothes that are piled on the floor. But that's the way you deal with people and you deal with organizations. That's the way every big organization runs."

Bloomberg lamented the loss of earmarking as a means for congressional cooperation.

"We've taken away some of that with these member items that used to be that Congress had a certain amount of money and they would bribe each legislator to vote for the important things. We got rid of that and now it's so fractured. It's hard to get anything through Congress."

He also said he'd raise interest rates if he were president and called for passing the Trans-Pacific Partnership trade deal, from which Trump ultimately withdrew the US.

In other comments, Bloomberg explained he backed Pennsylvania Republican Sen. Pat Toomey's reelection that year, even though he disagreed with him on most issues, because he supported his signature issue of guns. Democrats have criticized Bloomberg for his support of a small number of Republican candidates as late as the 2018 midterm elections.

He also criticized the "craziness of safe zones and triggers" on college campuses and the "fear of the unknown and how people react to it" for impacting intellectual diversity on campuses.

Bloomberg, who has championed local climate initiatives and given millions to the Sierra Club's campaign to combat climate change, also said in his remarks that the world should walk away from coal.

"Anything's better than coal, and then you push in the problem," he said. "What do you do with the poor coal miner who's out of a job? I understand that nobody's suggesting we shouldn't help the coal miner. But if I say to you, uh, Alex, there's 100,000 lives or maybe all the lives on the planet versus, you know, 200 jobs, it seems like an easy decision to make. I'm not suggesting we walk away from the coal miner. I'm suggesting you don't stop being intelligent and stop using the most polluting thing that we have in this country, in the world. And it's going to be a tough battle."

This story has been updated with comment from the Biden campaign.