George Santos, the embattled Republican congressman from New York who fabricated large swaths of his resume, admitted in an interview on Monday with Britain’s Piers Morgan that he had been a “terrible liar”.

Santos was elected to represent portions of the New York City borough of Queens and neighboring Long Island in November and a staggering number of falsehoods have come to light since. His lies include claiming to be Jewish, graduating from college, working at finance giants Citigroup and Goldman Sachs, and that his mother was in the World Trade Center during the Al-Qaida terrorist attack on 11 September 2001.

“I’ve been a terrible liar on those subjects,” Santos told the broadcaster and journalist Morgan in an interview on Talk TV. “What I tried to convey to the American people is I made mistakes of allowing the pressures of what I thought and needed to be done in order to … this wasn’t about tricking anybody.

“It wasn’t about tricking the people, this was about getting accepted by the party here locally.”

Santos pushed back, however, on the suggestion that he had lied about being Jewish.

“I never claimed to be Jewish. I’ve always made a party-favor joke. I’ve done it on stages across the country,” Santos said.

Morgan shot back: “What’s funny about falsely claiming you’re Jewish?”

Santos said: “Not falsely claiming I’m Jewish. I’d always say I’m Catholic but I come from a Jewish family so that makes me Jew-ish. It’s always been a party favor, everybody’s always laughed, and now that everybody’s cancelling me, everybody’s pounding down for a pound of flesh.”

Morgan replied: “Because you’re not Jewish.”

Santos also defended his comments on Judaism by pointing out that members of the Republican Jewish Coalition, an influential group, had found his comments funny when he spoke before them in November. He didn’t mention that the group has since denounced him and said Santos deceived them.

He also insisted that he had not lied about his mother’s presence in the South Tower of the World Trade Center in lower Manhattan on 9/11, when terrorists hijacked passenger jets into both of the edifice’s twin towers, even though the New York Times obtained records showing his mother, Fatima Devolder, was not in New York that day.

“Specifically on the point that nobody can find any evidence that your mother worked at the World Trade Center at all, ever, could you have just got this wrong?” Morgan said.

“Are you telling me that I got wrong what my mother told me?” Santos said. “She wasn’t one to mislead me.”

“There’s no record that she was there at all that day. There’s a record of every single person in both those towers,” Morgan said.

“I stay convinced that that’s the truth.”

Santos has faced calls to resign from Congress from his constituents and fellow Republicans, but has refused so far. He also faces federal and local investigations over his campaign finances. He recently resigned his membership on several congressional committees.