In his first public remarks, Frank G. Fina, the former deputy attorney general who launched the undercover operation, said he, too, favored an investigation.
"I think this is exactly what is needed, a third-party review of what I thought was an excellent case to determine the truth," said Fina, now a top prosecutor with the Philadelphia District Attorney's Office. "I welcome it."
Attorney General Kathleen G. Kane said Wednesday night that she, too, welcomed "the opportunity to work with the Ethics Committee."
In a statement, Kane was sharply critical of Fina.
"If this is such an 'excellent case,' perhaps Mr. Fina can explain why he didn't prosecute" the case either for the state or the Philadelphia District Attorney's Office, Kane said.
"And finally, perhaps Mr. Fina could offer his thoughts on why information surrounding this case, which has been dead for years, was recently leaked by anonymous sources. . . ."
In a letter Wednesday to the chamber's Committee on Ethics, House leaders said they would "make available sufficient resources" to ensure a thorough inquiry, should the committee authorize one.
That could include hiring an independent counsel to oversee an investigation that would have to be completed within 30 days.
"While none of the four have been charged with a crime," the letter said, "concerns exist about actions they are alleged to have taken."
The inquiry is expected to focus on the conduct of the House members - and not on Kane's controversial decision to abort the undercover operation shortly after she took office last year.
Kane said the operation was misconceived, poorly managed, and relied too heavily on an undercover operative whose credibility she said had been compromised by the fact that prosecutors dropped all charges against him in a $430,000 fraud case in exchange for his cooperation.
Supporters of the investigation say it was a solid operation run by experienced prosecutors that had ensnared several public officials and could have caught more.
The letter pledging support for an ethics inquiry was signed by House Speaker Sam Smith, a Jefferson County lawmaker who is the top Republican in the chamber, along with Mike Turzai of the Pittsburgh area, the majority leader.
Frank Dermody, the leader of the House Democrats, also signed.
In the chamber, there are 111 Republicans and 92 Democrats.
Previously, Dermody, also from the Pittsburgh area, seemed to focus on the fact that the lawmakers failed to disclose the gifts, not on their acceptance of the money in the first place.
"If it's true that any legislators accepted gifts without reporting them, they should correct that reporting mistake," Dermody said Monday.
Wednesday's letter, sent to the House Committee on Ethics, was triggered by a report in Sunday's Inquirer that a group of public officials, including four Democratic state representatives, had been tape-recorded accepting money or gifts. Kane said that as many as eight people had been targeted in the probe.
The House Committee on Ethics is empowered to investigate allegations involving the conduct of any of members of the House, and also that of lobbyists. Such an investigation would focus on whether House rules had been broken, such as the one prohibiting legislators from profiting from their office.
Rep. Scott Petri, a Bucks County Republican and the committee's cochair, said House rules prevented him from giving his personal views on whether there should be an investigation. Legislative sources, however, said Petri was eager to proceed.
Though the committee's hearings are not open to the public, its findings are. The eight-member committee, split evenly among Republicans and Democrats, could impose a penalty as harsh as censure, after which a member would no longer be allowed on the floor of the chamber or be permitted to vote on legislation.
No member has been censured in recent memory, House officials said.
The Inquirer has reported that the sting's key operative was Philadelphia lobbyist Tyron B. Ali, who agreed to go undercover in late 2010 and wear a body wire.
People with knowledge of the inquiry said those caught on tape included state Rep. Ron Waters, who accepted multiple payments totaling $7,650; Rep. Vanessa Brown, who took $4,000; Rep. Michelle Brownlee, who received $3,500; and Rep. Louise Bishop, who accepted $1,500.
Bishop has denied knowing Ali, or taking money from him. Brown has declined to comment. Brownlee has said she did not recall accepting money. And Waters has said he might have accepted something for his birthday.
The sting was launched by top state prosecutors in October 2010, when Gov. Corbett was attorney general.
However, Kane said she believed the investigation was badly managed and possibly marred by racism, factors that would have made it difficult for prosecutors to win the cases in court.
Prosecutors who handled the undercover operation have countered that Fina ran a quality investigation that they say Kane, a Democrat, abandoned for political reasons.