George Santos, the New York Republican congressman-elect at the center of a storm over his apparently fabricated résumé, has admitted he lied about his job experience and college education during his successful US House campaign.

Santos first ran for Congress in 2020. In November this year he was elected to represent parts of northern Long Island and north-east Queens.

His exaggerations were first identified by the New York Times, which questioned claims including that he had worked at two prominent Wall Street banks; had obtained degrees in finance and economics from two New York colleges; that he was Jewish; and that four employees of his company were killed in the Pulse nightclub shooting in Orlando, Florida, in June 2016.

On Monday, Santos told the New York Post: “My sins here are embellishing my résumé. I’m sorry.”

Santos, 34, also said he “campaigned talking about the people’s concerns, not my résumé … I intend to deliver on the promises I made during the campaign”.

But he acknowledged he “didn’t graduate from any institution of higher learning. I’m embarrassed and sorry for having embellished my résumé. I own up to that. … We do stupid things in life”.

Democrats including the House speaker, Nancy Pelosi, have suggested Santos is unfit to sit in Congress. Some have called for him to resign his seat before taking it.

Ted Lieu, a California Democrat, said on Twitter: “George Santos, who has now admitted his whopping lies, should resign. If he does not, then [Kevin McCarthy, the Republican House leader] should call for a vote to expel” him.

Joaquin Castro, from Texas, said allowing Santos to enter office would set a dangerous precedent.

“We’ve seen people fudge their résumé but this is total fabrication,” Castro said, suggesting Santos “should also be investigated by authorities”.

Hakeem Jeffries, the incoming Democratic House leader, has said Santos “appears to be a complete and utter fraud”.

Republican officials began to publicly respond to Santos’ remarks on Tuesday. Joe Cairo, chairman of the Nassau county GOP on Long Island, said the congressman had “broken the public trust” but “must do the public’s will in Washington”.

Santos, Cairo said, “has a lot of work to do to regain the trust of voters and everyone who he represents in Congress”.

Santos said he worked for Citigroup and Goldman Sachs. Neither company could find relevant records. Santos told the Post he “never worked directly” for either firm and had used a “poor choice of words”. He said LinkBridge, an investment company where he was a vice-president, did business with both.

The Times also uncovered Brazilian court records showing Santos was once charged with fraud for using a stolen checkbook.

“I am not a criminal here – not here or in Brazil or any jurisdiction in the world,” Santos told the Post. “Absolutely not. That didn’t happen.”

Santos said he experienced financial difficulties that left him owing landlords and creditors.

Another news outlet, the Jewish American site the Forward, questioned a claim on Santos’s website that his grandparents “fled Jewish persecution in Ukraine, settled in Belgium and again fled persecution” during the second world war.

“I never claimed to be Jewish,” Santos said. “I am Catholic. Because I learned my maternal family had a Jewish background I said I was ‘Jew-ish’.”

Cairo said: “The damage that his lies have caused to many people, especially those who have been impacted by the Holocaust, is profound.”

The Daily Beast has reported that Santos, who has identified as gay, was divorced from a woman in September 2019.

“Though the past marriage isn’t necessarily at odds with his sexuality,” the site noted, Santos has never acknowledged that relationship and his biography says he lives with his husband, Matt, and four dogs.

“I dated women in the past. I married a woman. It’s personal stuff,” Santos told the Post, adding that he was “OK with my sexuality. People change”.

Revising claims that a company he worked for “lost four employees” in the Pulse nightclub shooting, Santos said the four were in the process of being hired.