George Santos – the New York Republican congressman under local, state, federal and international investigation over his largely made-up résumé, suspect campaign finances and potentially criminal aspects of his personal history – “will get seated on committees”, the US House speaker said on Tuesday.

Speaking to reporters at the Capitol, Kevin McCarthy said: “We will be done with all committees today – he will get seated on committees.”

McCarthy must govern with a narrow majority, 222-213. Earlier this month, Santos supported McCarthy through 15 votes for speaker.

McCarthy has deflected growing calls for Santos to resign, from Republicans in New York’s third congressional district and on Capitol Hill from senior Democrats.

Instead, McCarthy and other Republicans have said the New York freshman should be subject to a House ethics process the party is trying to gut.

Santos’s résumé has been shown to be largely fictional, including claims about where he went to college, which companies he worked for, and his racial and family background.

Democrats and an outside watchdog have called for an investigation of Santos’s campaign finances. He is under investigation at local and state levels in New York, by US federal authorities and by authorities in Brazil, in that case over the use of a stolen chequebook.

On Monday, the Washington Post extended the story to Russia, reporting that Santos “has deeper ties than previously known” to Andrew Intrater, “a businessman who cultivated close links with a onetime Trump confidant and who is the cousin of a sanctioned Russian oligarch”.

Intrater is related to Viktor Vekselberg, a billionaire in the Russian energy industry. Intrater’s links with Michael Cohen, then Trump’s lawyer and fixer, came under the gaze of Robert Mueller, the special counsel who investigated Russian election interference and links between Trump and Moscow.

Santos has admitted to “embellishing” his résumé but denied wrongdoing and insisted he will not resign.

Democrats have raised questions about how much McCarthy and other Republicans knew of Santos’s falsehoods before he won last November.

On Sunday, Daniel Goldman told CBS that he and another New York Democrat, Ritchie Torres, had written to McCarthy, his lieutenant Elise Stefanik and the head of McCarthy’s Super Pac about “bombshell … reporting from the New York Times that they all knew about Mr Santos’s lies prior to the election”.

On Monday, McCarthy told reporters: “I never knew about his résumé or not but I always had a few questions about it.”

The Times report said that in 2021 a member of Santos’s staff pretended to be McCarthy’s chief of staff.

On Tuesday, McCarthy said: “My staff had concerns when he had a staff member impersonate my chief of staff and that individual was let go when Mr Santos found out about it.”

In a column for NBC News, meanwhile, Torres said that having grown up across the street from former president Donald Trump’s “gilded golf course, I know what it’s like to have the neighbourhood you love hijacked by a man who is deceitful to the core”.

“Now”, Torres added, “as I begin my second term in Congress representing the good people of the Bronx, I find myself in an institution that I love hijacked by yet another liar, cheat and fraud.”