Americans are facing an “epidemic of dishonesty” in Washington that is more dangerous than terrorism or communism, according to former New York City mayor Michael Bloomberg.

In a commencement speech on Saturday at Rice University in Houston, the billionaire said “an endless barrage of lies” and a trend toward “alternate realities” in national politics pose a dire threat to US democracy.

The 76-year-old, who flirted with an independent presidential run in 2016, did not call out any politicians by name. Although he derided Donald Trump as “a con” and a “dangerous demagogue” before his election, in an interview before the speech at Rice Bloomberg refused to comment specifically on the president. Fact checkers have determined that Trump has made hundreds of false and misleading statements since entering the Oval Office.

“This is bigger than any one person,” Bloomberg said. “It’s bigger than any one party.”

In his speech, Bloomberg evoked the legend of the nation’s first president, George Washington, who as a boy supposedly said he could not tell a lie when asked if he cut down a cherry tree.

“How did we go from a president who could not tell a lie to politicians who cannot tell the truth?” Bloomberg asked. He blamed “extreme partisanship” for an unprecedented tolerance of dishonesty in US politics and said people were now committed more to their political tribes than the truth, suggesting that the nation is more divided than any time since the civil war.

“There is now more tolerance for dishonesty in politics than I have seen in my lifetime,” Bloomberg said. “The only thing more dangerous than dishonest politicians who have no respect for the law is a chorus of enablers who defend their every lie.”

For example, he noted that Democrats spent much of the 1990s defending President Bill Clinton against charges of lying and personal immorality, just as Republicans attacked the lack of ethics and honesty in the White House. The reverse is happening today, he said.

In one jab at Trump, he noted that the vast majority of scientists agree that climate change is real. Trump and his Republican allies have repeatedly called climate change a hoax promoted by America’s adversaries.

“If 99% of scientists whose research has been peer-reviewed reach the same general conclusion about a theory, then we ought to accept it as the best available information – even if it’s not a 100% certainty,” Bloomberg said. He added, in a direct reference to Trump’s past remarks: “That, graduates, is not a Chinese hoax.”

He warned that such deep levels of dishonesty could enable what he called “criminality”. Asked what specifically he meant, Bloomberg noted “lots of investigations” going on, but he declined to be more specific.

Several Trump associates are facing criminal charges as part of a federal investigation into Russia’s meddling in the 2016 election. Three have pleaded guilty to making false statements to the FBI. Federal investigators want to interview Trump himself, although the president’s legal team has resisted so far.

“When elected officials speak as though they are above the truth, they will act as though they are above the law,” Bloomberg told graduates. “And when we tolerate dishonesty, we get criminality. Sometimes, it’s in the form of corruption. Sometimes, it’s abuse of power. And sometimes, it’s both.

“The greatest threat to American democracy isn’t communism, jihadism, or any other external force or foreign power. It’s our own willingness to tolerate dishonesty in service of party, and in pursuit of power.”