June 17 (Bloomberg) -- Nevada Senator John Ensign resigned from a Republican leadership position a day after admitting he had an extramarital affair with a campaign aide.

Ensign stepped down as chairman of the Senate Republican Policy Committee, the fourth-ranking party leadership position in that chamber, Senate Minority Leader Mitch McConnell said in a statement released by his office.

“He’s accepted responsibility for his actions and apologized to his family and constituents,” said McConnell, a Kentucky Republican. “He offered, and I accepted, his resignation as chairman of the policy committee.”

Ensign’s spokeswoman, Jennifer Cooper, also confirmed his resignation and said there was no further statement.

Ensign, 51, told reporters in Las Vegas yesterday the affair was “the worst thing I have ever done in my life.”

Ensign, who was chairman of the National Republican Senatorial Committee last year, said yesterday, “I am committed to my service in the United States Senate and my work on behalf of the people of Nevada.”

The one-time veterinarian was first elected to the Senate in 2000 and re-elected, with 55 percent of the vote, in 2006. He previously served four years in the U.S. House.

“I take full responsibility for my actions,” he said yesterday. “I know that I have deeply hurt and disappointed my wife, Darlene, my children, my family, my friends, my staff and others who believed in me.” Ensign said he and his wife underwent marriage counseling and have “rebuilt our marriage.”

‘Close Friends’

The senator wouldn’t identify the woman with whom he had the affair, except to say their families were “close friends” and that the woman and her husband had “worked for me.” Cooper said in an e-mail the woman was a member of Ensign’s campaign staff.

Ensign was one of the first Senate Republicans in 2007 to call for the resignation of then-Senator Larry Craig of Idaho when the Republican lawmaker pleaded guilty to misdemeanor disorderly conduct after police accused him of soliciting sex in a bathroom at the Minneapolis-St. Paul International Airport.

“He did plead guilty” to “lewd behavior, basically in a public restroom, and that’s not the kind of behavior” a “United States senator should be engaged in,” Ensign said in an Oct. 17, 2007, interview on CNN.

To contact the reporters on this story: Jonathan D. Salant in Washington at jsalant@bloomberg.net; James Rowley in Washington at jarowley@bloomberg.net.

Last Updated: June 17, 2009 13:21 EDT