The New York Republican congressman George Santos, who is at the centre of a bizarre string of scandals and who the Utah senator Mitt Romney this week called a “sick puppy”, was charged with theft in Pennsylvania in 2017 – over a purchase of “puppies”.

The scandal, reported by Politico, is not Santos’s first involving dogs and his charity, Friends of Pets United. A New Jersey veteran alleges Santos raised money for an operation for his dog, then absconded with the money.

In the Pennsylvania case, in Amish Country, $15,125 in bad checks were made out for “puppies”, Politico reported.

Days later, Santos held an adoption event at a Staten Island pet store. Citing court records and a lawyer who helped Santos, Politico said the theft charge was dropped and Santos’s record expunged, after Santos said someone had stolen his checkbook.

It is not Santos’s first case involving a checkbook. Prosecutors in Brazil have reopened a case involving the alleged use of a stolen checkbook.

Santos denies all alleged wrongdoing and says he will not resign. He did not comment about the Amish Country case. The lawyer, Tiffany Bogosian, told Politico “she now doesn’t believe” his story, given subsequent developments.

Bogosian told the New York Times: “I should have never got involved. He should have went to jail. And I wish nothing but bad things for him.”

Santos, 34, won in New York’s third district last year. He has since admitted embellishing his résumé.

Bizarre claims, including playing volleyball for a college he didn’t attend and being a producer on the Spider-Man musical, have been exposed. Claims about his family, including descent from Holocaust survivors and that 9/11 “claimed” his mother’s life, have been disproven. Santos has denied reports he was a drag queen in Brazil.

He has also been accused of sexual harassment, by a former aide. His charity is being investigated.

Republicans, Democrats and constituents have called for Santos to quit. But Santos supported Kevin McCarthy through 15 votes for House speaker and the Republican leader, who must work with a narrow majority, has not said Santos should go.

McCarthy and other senior Republicans have said they are waiting on investigations of Santos’s campaign finance filings, amid questions about the source of his wealth and activities under a different name, Anthony Devolder.

Resignations from Congress are common but expulsions are not. Only five representatives have been expelled – three for fighting for the Confederacy in the civil war. Regardless, on Thursday Democrats filed a resolution for Santos’s expulsion.

“We gave him plenty of time to resign and he has chosen not to do so,” said Robert Garcia of California.

Santos said again he would not resign voluntarily.

Romney’s clash with Santos came at the State of the Union address on Tuesday.

Romney said he told Santos he did not belong in Congress. He also called Santos a “sick puppy” and poured scorn on his résumé claims. Santos claimed Romney called him an “ass” and to have called the senator an “asshole”.

On Thursday, Santos told Newsmax that the same night, the independent Arizona senator Kyrsten Sinema was “very polite, very kindhearted” and said: “Hang in there buddy.”

On Friday, a spokesperson for Sinema told CNN: “This is a lie.”