The Republican frontrunner for Arizona's U.S. Senate seat is finding himself under attack by Democrats for omitting from his campaign website his work more than a decade ago as a lobbyist for a mining company in Namibia.

Rep. Jeff Flake (R) acknowledged in a National Journal article last month that in the 1990s he worked as a lobbyist for Rossing Uranium, a mining company with ties to Iran, a position he kept relatively quiet. National Journal reported that Flake registered as a foreign agent during this period. In an interview with the Associated Press last week, Flake said he has been upfront about his work as a lobbyist for the mining company.

"I have mentioned it in bios, I have mentioned it in numerous speeches. So this notion that I tried to hide my past is farcical," Flake told the AP.

Flake's biography on his campaign website for his 2000 race for Congress acknowledges that he "represented Namibian companies" in Washington for a period in the 1990s after he headed an organization advocating for Namibian independence.

"Following Namibian independence in 1990, Jeff and Cheryl moved back to Washington, D.C., where Jeff represented Namibian companies for the next two years," the 2000 campaign website said.

Flake's 2004 campaign website did not cite his lobbyist work in his bio, however. The Internet Archive Wayback Machine has archived material from Flake's website from shortly after his 2000 election and starting in 2004.

Flake told National Journal that he did not know the company was partially owned by Iran and that his work with the company did not play a role in congressional votes he cast on Iranian issues. Flake told National Journal that he was paid $7,000 a month to lobby for the company.

Flake said that his interest in African issues came from his work as a Mormon missionary in southern Africa as a teen. During his congressional career, Flake has identified himself as "a Washington outsider."

His campaign spokesman, Andrew Wilder, did not return multiple messages for comment left on his cell phone. The current Senate campaign website biography does not mention the Namibian work.

Flake is locked in a Republican Senate primary with businessman Will Cardon, who has come out against Flake's work as a lobbyist and has described the six-term congressman as a "Washington insider." The winner of the primary faces Democrat Richard Carmona, a former U.S. surgeon general, in November. Carmona's background as a Bush administration appointee and moderate Democrat has made the open-seat race competitive. Arizona political insiders have said that details of Flake's lobbying work were not that well known prior to recent reports.

Democrats have been quick to attack Flake on his work.

"Jeff Flake is the definition of a Washington, D.C. insider. He spent years as a Washington lobbyist and a registered foreign agent, doing the bidding of special interest foreign clients before becoming a career politician who voted to benefit his former clients. Worst of all, Flake tried to hide his lobbying, his lobbying past and possible conflicts of interest from Arizonans,” said Matt Canter, spokesman for the Democratic Senatorial Campaign Committee.