The former New York mayor Rudy Giuliani’s troubles deepened on Friday when he was suspended by WABC radio, for trying to use his show to discuss the lie that the 2020 presidential election was lost by Donald Trump because of electoral fraud.

John Catsimatidis, a New York billionaire, Republican donor and owner of WABC, told the New York Times: “We’re not going to talk about fallacies of the November 2020 election. We warned him once. We warned him twice. And I get a text from him last night, and I get a text from him this morning that he refuses not to talk about it.

“So he left me no option. I suspended him.”

A spokesperson for Giuliani did not immediately respond to a request for comment.

Now 79, Giuliani was mayor of New York from 1993 to 2001, emerging as a national figure after leading the city through the 9/11 terror attacks. He ran for the Republican presidential nomination in 2008 but flopped.

Long close to Trump, who reportedly helped him through a personal crisis after the failed presidential run, Giuliani emerged as a steadfast supporter when Trump ran for the Republican nomination in 2016 and then won the White House.

Giuliani did not win the prize of being made secretary of state, but he worked on Trump’s behalf in matters including the attempt to extract political dirt from Ukraine, which prompted Trump’s first impeachment.

In 2020, Giuliani worked to try to overturn Joe Biden’s defeat of Trump at the polls, only to suffer a series of courtroom defeats and mounting public embarrassments.

Giuliani denies wrongdoing, but his efforts on Trump’s behalf have produced legal disbarment proceedings; criminal charges in two swing states, Georgia and Arizona; and defeat in a defamation suit that left him owing $148m to two Georgia poll workers he claimed were involved in electoral fraud.

Giuliani filed for bankruptcy in New York last December. Filings showed debts of up to $500m.

Earlier this week, a legal filing on Giuliani’s behalf said no accountants “seem[ed] interested” in working with him to meet requirements in the bankruptcy case.

His spokesperson, Ted Goodman, said then: “While it is true that the permanent Washington political class is leveraging all of its power and influence to bully and scare people from defending Americans who are willing to stand up and push back against the accepted narrative, Mayor Giuliani will be appropriately represented when it comes to his accounting and finances.”

The filing on Tuesday said the former mayor, who made millions in consulting work after leaving office in 2001, “currently received social security benefits and broadcasts a radio show and podcast”.

“These are his sole sources of income,” it said.

Catsimatidis told the Times that at the close of his WABC show on Thursday, Giuliani tried to speak about the 2020 election but was cut off by station employees.

“Look, I like the guy as a person, but you can’t do that,” Catsimatidis told the paper. “You can’t cross the line. My view is that nobody really knows [about the 2020 result] but we had made a company policy.

“It’s over, life goes on.”