Former Environmental Protection Agency Administrator Lisa Jackson denied circumventing federal record law by using secret email addresses in testimony before the House Committee on Oversight and Government Reform Tuesday.

Jackson, who announced her resignation in December and is now the chief environmental officer at Apple, has been in the crosshairs of congressional GOP investigators since it was discovered last year that she used a secondary EPA email address under the alias "Richard Windsor."

Further emails disclosed through the Freedom of Information Act (FOIA) revealed Jackson also used her private home email to correspond with a lobbyist for the multinational company Siemens.

In her prepared statement and during questioning by members of congress, Jackson fought back against the allegations of secrecy that have dogged her even after she left the EPA for a private-sector job.

"I have come to accept that there are those who will second-guess the judgments that I made or question the motives behind those judgments," Jackson said. "The principle reason I wanted to come here today is to make it perfectly clear that it was my practice to ensure that any official business conducted by me or through my email accounts was appropriately captured for record keeping purposes."

Critics accused Jackson of using her secondary email address to skirt open-records law and keep sensitive communications from appearing in FOIA disclosures.

"Officials in multiple Administrations have struggled to fully comply, and in some instances willfully flaunted, federal transparency and record keeping laws through their use of non-official e-mail and other electronic communications to conduct official government business," Oversight chairman Darrell Issa (R., Calif.) said in a statement announcing the hearing.

Testifying before the committee, Jackson said her "Richard Windsor" account was set up at the advice of career staffers, who advised her to choose an alias, rather than any reference to herself that could be guessed.

High-level officials have used secondary email addresses stretching back several administrations as a way to manage the flood of email they receive, Jackson said. She also said she and the agency went to lengths to ensure the account was included in FOIA disclosures—a chief concern of transparency watchdogs.

Jackson characterized the Siemens lobbyist Alison Taylor, whom she sent emails to, as a friend and said their interactions were not business-related.

"I believe personal friends should use personal emails," Jackson told Rep. Trey Gowdy (R., S.C.).

"I was telling a personal friend, ‘Hey, if you want to … contact me at home,’" Jackson continued.

"I apologize, but that was what the Abramoff scandal was about," Issa said. "People said they were friends, but he was a lobbyist."

As first reported by the Washington Free Beacon, Jackson has retained a lawyer to counsel her in a continuing congressional investigation that shows no signs of slowing.

Sen. David Vitter (R., La.) and Republicans on the Senate Environment and Public Works Committee released a scathing report on Monday, charging that the EPA under Jackson’s leadership had a "developed a culture of secrecy and evasion."

In addition to Jackson, the report detailed several other EPA officials using private email addresses to conduct government business and charged the agency with biased handling of FOIA requests.

"Ultimately, the purpose of using secret emails, personal emails, applying excessive redactions to documents released via FOIA, and erecting other barriers to transparency is to avoid scrutiny and accountability," the report said.

"These actions were taken contrary to official EPA policy and sometimes, contrary to the law. While in some instances the Agency has begrudgingly admitted their mistakes, the culture of secrecy runs deep, and it will take the proactive intervention of EPA’s new leadership to right the ship and require the transparency the President promised the American people."

The National Archives and Records Administration released a bulletin on Monday restating record-keeping requirements for federal employees.

Federal employees are discouraged from using private email to conduct government business, and if they do, they are required to send copies to their official account for record-keeping purposes.