Homeland Security Deputy Secretary Alejandro Mayorkas told lawmakers Thursday he regrets creating a perception of favoritism by getting involved in foreign investor visa cases involving prominent Democrats while head of U.S. Citizenship and Immigration Services.

But the department's No. 2 official said that he stands by his decision to take part in the cases, telling lawmakers on the House Homeland Security Committee that he was involved in "more cases (visa) than I can count" to help ensure that the agency was doing its job.

"I regret the perception my own involvement created," Mayorkas told lawmakers. "I did my job and fulfilled my responsibility,"

Mayorkas is testifying about a report from his agency's inspector general that concluded he violated ethics rules when he intervened as head of USCIS in three foreign-investor visa cases involving prominent Democrats.

Inspector General John Roth didn't accuse Mayorkas of breaking the law when he intervened in the three cases that were part of the U.S. government's investor-visa program, known as EB-5. But he said that Mayorkas violated agency rules that he drafted as head of USCIS.

Thursday offered the first chance lawmakers have had to question Mayorkas about the 99-page report from March.

Committee Chairman Michael McCaul said the report raised serious questions about Mayorkas's role as director of USCIS and he plans to investigate the agency's foreign investor visa program further.

"There may be nothing there, but I think it warrants further review," McCaul said. "I think you also violated your own ethics policy. Political appointees should be held to the same ethical standards, I believe, as the rank and file."

Rep. Bennie Thompson, the top Democrat on the committee, said Thursday that Roth's report was incomplete and didn't highlight that Mayorkas was responsive to both Republicans and Democrats.

"I am disappointed that, after expending months of resources to investigate these cases, the inspector general produced an incomplete report," the Mississippi Democrat said.

Roth found that Mayorkas improperly meddled with three visa cases involving the youngest brother of Democratic presidential candidate Hillary Rodham Clinton, Virginia Gov. Terry McAuliffe, former Pennsylvania Gov. Ed Rendell and Senate Democratic Leader Harry Reid of Nevada.

At a March hearing in front of McCaul's committee, Roth told lawmakers that "in each of these three instances, but for Mr. Mayorkas' intervention, the matter would have been decided differently."

Mayorkas was accused of intervening in applications for the government's EB-5 visa program, which allows foreigners to obtain visas to live permanently in the United States with their spouse and children if they invest $500,000 to $1 million in projects or businesses that create jobs for American citizens. Approved investors can become permanent residents after two years, and later can become U.S. citizens.

Mayorkas has steadfastly denied any wrongdoing since the allegations first surfaced days before his July 2013 Senate confirmation hearing. The investigation was first reported by The Associated Press and prompted a boycott of his hearing by Senate Republicans, including Sen. Charles Grassley of Iowa.

During that hearing, Mayorkas called the allegations "unequivocally false." After Roth's report was made public, Mayorkas said he disagreed with the findings but said, "I will certainly learn from it and from this process."

He added: "There was erroneous decision-making and insufficient security vetting of cases. I could not and did not turn my back on my responsibility to address those grave problems. I made improving the program a priority and I did so in a hands-on manner."

Grassley, who chairs the Senate Judiciary Committee, has called for Mayorkas to be held accountable for Roth's findings, but has stopped short of calling for his firing.