The Republican George Santos said on Wednesday he would not resign from Congress less than a week after being sworn in, despite calls to do so from the chairman of his district committee and a fellow New York representative, amid continuing scrutiny of Santos’s mostly made-up résumé and growing calls for campaign finance investigations.

In a tweet, Santos said: “I was elected to serve the people of the New York third district not the party and politicians, I remain committed to doing that and regret to hear that local officials refuse to work with my office to deliver results to keep our community safe and lower the cost of living.

“I will NOT resign!”

He was responding to remarks to reporters by Joseph Cairo, chair of the Nassau county Republican committee, who said Santos ran “a campaign of deceit, lies and fabrication” to win the third district last year.

At the same time, a first sitting Republican congressman, Anthony D’Esposito, also of New York, called on Santos to quit.

Santos has faced a barrage of negative coverage.

He has admitted to “embellishing” his résumé, including lying about his college record – he did not attend Baruch and New York University – and saying a “poor choice of words” created the impression he worked for Citigroup and Goldman Sachs.

He has claimed a tragic link to the Pulse nightclub shooting and said the attacks on New York on 11 September 2001 “claimed my mother’s life”. His mother died in 2016.

He has claimed to have Jewish roots and to be descended from Holocaust survivors.

He is under investigation in New York and in Brazil, in the latter case over the use of a stolen chequebook.

His Democratic predecessor in the third district has called him a “conman”.

Cairo said Santos “deceived the voters of the third congressional district, he deceived the members of the Nassau county Republican committee, elected officials, his colleagues, candidates, his opponents and even some of the media.

“His lies were not mere fibs. He disgraced the House of Representatives. In particular, his fabrications went too far. Many groups were hurt. Specifically, those families that were touched by the horrors of the Holocaust. I feel for them.

“He has no place in the Nassau county Republican committee, nor should he serve in public service nor as an elected official. He is not welcome here at Republican headquarters for meetings or at any of our events. As I said, he’s disgraced the House of Representatives, and we do not consider him one of our congresspeople.

“Today, on behalf of the Nassau county Republican committee. I am calling for his immediate resignation.”

In his own statement, to Politico, D’Esposito said Santos’s “many hurtful lies and mistruths … have irreparably broken the trust of the residents he is sworn to serve. For his betrayal of the public’s trust, I call on [him] to resign”.

Santos was sworn into Congress last weekend, almost a week late after backing Kevin McCarthy, the House Republican leader, through 15 votes for speaker.

Casting one vote, Santos appeared to flash a “white power” sign. He has previously claimed to be partly Black. He also told the New York Post he was “Catholic. Because I learned my maternal family had a Jewish background I said I was ‘Jew-ish’.”

Another newly elected New York Republican, Nick LaLota, has called for an investigation. On Tuesday, two New York Democrats who hand-delivered a request for an ethics investigation of Santos, Daniel Goldman and Ritchie Torres, said they had heard from Republicans who supported such a step.

But Republican leaders have not acted.

On Tuesday, Politico reported that Republicans were discussing what to do. Santos told the site he expected to be given committee assignments. On Wednesday, asked if Santos would sit on top committees, McCarthy said: “No.”

Seizing on Cairo’s remarks, Jaime Harrison, chair of the Democratic National Committee, tweeted that McCarthy’s “spine found a new home in Nassau county”.

Harrison added: “It is shameful that a New York county party chair has to protect and defend the honor of the House of Representatives against the lies of Santos while McCarthy is too scared to even utter his name.”

In Washington on Tuesday, Goldman and Torres delivered to Santos their demand for an investigation by the House ethics committee.

Goldman, like Santos elected last November, said: “Santos, we have a complaint for you.”

Santos said: “Sure.”

In their complaint, Goldman and Torres cited “extensive public reporting – as well as Santos’s own admissions … that Mr Santos misled voters in his district about his ethnicity, his religion, his education, and his employment and professional history, among other things”.

They requested an investigation of Santos for “failing to file timely, accurate and complete financial disclosure reports as required by law”.

Santos’s campaign finances are the subject of a complaint filed with the Federal Election Commission by the Campaign Legal Center (CLC), a non-partisan watchdog.

The CLC complaint questions the source of Santos’s personal wealth and the propriety of loans to his own campaign.

Torres and Goldman called Santos’s financial reports for a failed run in 2020 and his win in 2022 “sparse and perplexing”, adding: “At a minimum it is apparent he did not file timely disclosure reports for his most recent campaign.”

They wrote: “If Mr Santos’s 2020 and 2022 financial disclosures are to be believed, his salary increased from $55,000 in 2020 to $750,000 in 2021 and 2022, of which he gave a whopping $705,000 to his campaign.

“The committee should investigate the veracity of these claims and whether Mr Santos has engaged in fraudulent activity.”

Santos told reporters that though Goldman and Torres were “free to do whatever they want to do”, he was not concerned, as he had “done nothing unethical”.

Asked if he had done anything wrong, he said: “I have not.”

Torres and Goldman also said Santos had “failed to uphold the integrity expected of members of the House of Representatives”.