A member of the House Intelligence Committee is calling on Donald Trump’s personal lawyer, Rudy Giuliani, to disclose information on who financed his attempts to dig up dirt on Joe Biden amid a wave of reports that the work has dovetailed into official government business.

“Rudy needs to disclose his clients for the Ukraine work,” said Rep. Sean Patrick Maloney (D-NY). “He’s up to his neck in criminals and dirty money. Was he playing the President to get himself paid? Seems there’s no honor among thieves.”

It’s unclear if Giuliani’s finances have been a component of House Democratic investigations into the pressure campaign that the former New York City mayor and President Trump applied to Ukrainian leadership in order to persuade them to investigate the work Biden’s son, Hunter, was doing in that country. But CNN reported that his financial dealings are under renewed scrutiny by investigators following the arrests of two clients, Soviet-born businessmen Igor Fruman and Lev Parnas, on Thursday for campaign finance violations. And Maloney’s comments suggest that there is an appetite for congressional investigators to better understand the money-trail as well.

In an interview with The Daily Beast this week, Giuliani steadfastly denied that he was paid for any work he did in Ukraine, saying that he helped Trump on a “pro bono” basis. He said that the costs of his travel were covered by private clients for separate work that happened to correspond with his Ukraine portfolio. Speaking specifically about an August trip he made to Madrid to urge Andriy Yermak, a top Ukrainian official, to reinvestigate the Bidens, Giuliani said that he happened to be going to the Spanish capital already for “business and vacation.”

“I have law clients and I have security clients in London and Madrid,” he said. “And that particular trip has not been reimbursed but about three-fourths of it would be business and one-fourth would be personal. The Trump part would be considered personal because I don't get paid for representing the president.”

Giuliani also said that he never charged the State Department for the work he did to meet with and talk to Ukrainian officials, including Yermak.

“I've done work for the State Department before and I never charged them for it,” he said. “They call upon citizens all the time. I did it at least three times with [former Secretary of State] Colin Powell... I did this as a service to my government.”

The extent of the work Giuliani did with and for the State Department has become a central component of the ongoing impeachment drama that has roiled the Trump administration. Text messages revealed during the course of congressional investigations showed that top officials at Foggy Bottom leaned on the former mayor to get a better sense of how the newly elected Ukrainian leadership was operating. But Giuliani also played a role in feeding State highly conspiratorial, and largely discredited information about Ukraine supposedly playing a role in the launch of the special counsel probe into 2016 election meddling and Hunter Biden’s post on the board of a natural gas company in that country.

Giuliani’s private clients also appear to have gotten preferential treatment from the president. On Wednesday, Bloomberg reported that Trump pressed his then-Secretary of State Rex Tillerson to encourage the Department of Justice “to drop a criminal case against an Iranian-Tukrish gold trader who was a client of Rudy Giuliani.” And last week, the Associated Press reported that at the same time Giuliani was trying to persuade Ukrainian leaders to launch investigations, individuals with ties to the former mayor were “trying to install new management at the top of Ukraine’s massive state gas company”—all while touting their connections to Trump and Giuliani.

Giuliani called the AP article “totally false” and a “Biden-inspired hit job.”

“I haven't done anything in Ukraine in two years. I have never done a deal in Ukraine,” he said. “I haven't even thought about a deal in Ukraine over the last two years.”

But government ethicists and watchdogs have said that the opaqueness around Giuliani’s finances does raise alarms about whether the president’s lawyer is acting in a formal diplomatic capacity or as a conduit for private interests.

“Giuliani is acting as this unofficial envoy at times with the apparent backing of the State Department, so he’s in this quasi-official diplomatic role representing the interests of the U.S. government,” said Brendan Fischer, the director of federal and FEC reforms for the Campaign Legal Center. “But he’s not subject to any of the ethics obligations that would attach to a federal government employee, most notably financial disclosure forms.”

Fischer noted that one particular area where Giuliani could be pressing the boundaries of the law related to whether he has provided a material benefit to the Trump re-election campaign for which he either was not reimbursed or for which a foreign actor provided the reimbursement. The matter was tricky, Fischer conceded, because Giuliani is not technically working for the re-election campaign even though there are a “number of areas where his claims of personal work intersect with the campaign.”

Asked directly to respond to the idea that he may have pushed the boundaries—if not outright violated—the limits of campaign finance law, Giuliani insisted that it was impossible because his work in Ukraine ended before Biden formally announced his presidential bid.

“Are you kidding me, a campaign finance violation?” he responded. “It is an absolutely stupid question. Quote this: ‘Nobody would ask such a stupid question unless they were in the tank for Joe Biden and the Democratic Party.’”