Representative Rick Renzi, a Republican who represents a vast region of Arizona, has been indicted on charges of using his office to enrich himself through a complex land swap scam, federal prosecutors announced on Friday in Phoenix.

Representative Rick Renzi, a Republican who represents a vast region of Arizona, has been indicted on charges of using his office to enrich himself through a complex land swap scam, federal prosecutors announced on Friday in Phoenix.

The prosecutors said a grand jury on Thursday returned a 35-count indictment accusing Mr. Renzi, 49, and two former associates of extortion, wire fraud, money-laundering and various conspiracies that could bring many years in prison and fines of hundreds of thousands of dollars upon conviction.

The indictment asserts that Mr. Renzi was in financial trouble in 2005 “and needed a substantial infusion of funds to keep his insurance business solvent and to maintain his personal lifestyle.” The Congressman, who announced last August that he would not seek a fourth term, and his wife, Roberta, have 12 children.

Prosecutors say Mr. Renzi misused his position on the House Natural Resources Committee to shepherd legislation enabling investors to swap tracts of property for land owned by the federal government — but only if they would include land owned by James W. Sandlin, a real estate investor from Sherman, Tex., in the deal.

“No Sandlin property, no bill,” the Congressman allegedly said in 2005, meaning he would block the bill if Mr. Sandlin were not included in the profitable deal. The deal netted Mr. Sandlin some $4.5 million, prosecutors say.

Mr. Sandlin, who was also indicted on the extortion, fraud, money-laundering and conspiracy charges, was a heavy contributor to Mr. Renzi’s first campaign in Arizona’s First Congressional District, in 2002. The indictment said that Mr. Renzi and Mr. Sandlin concealed at least $733,000 that the Congressman took for helping the lucrative land deal go through.

“Congressman Renzi misused his public office by forcing a land sale that would financially benefit himself and a business associate, and in so doing, he betrayed the trust of the citizens of Arizona,” said the United States attorney for Arizona, Diane J. Humetewa.

Mr. Renzi and another defendant, Andrew Beardall, 36, of Rockville, Md., are also accused of embezzling more than $400,000 in premiums from an account in an Arizona insurance business owned by the Renzi family to help finance Mr. Renzi’s first Congressional campaign.

Mr. Renzi has long denied wrongdoing and has called himself the victim of “leaked stories, conjecture and false attacks.”