Representative Henry Cuellar, Democrat of Texas, and his wife were charged with participating in a yearslong $600,000 bribery scheme involving Azerbaijan and a Mexican bank, according to a federal indictment unsealed in Houston on Friday.

Mr. Cuellar, 68, and his wife Imelda, 67, are accused of bribery and money laundering in connection with their efforts on behalf of a bank based in Mexico City and an energy company owned by Azerbaijan, according to the 54-page complaint.

Mr. Cuellar is also accused of acting as an agent of a foreign entity while serving as a U.S. government official.

Payments made from 2014 to 2021 were laundered through “sham consulting contracts,” front companies and shell companies owned by Mrs. Cuellar, who performed “little to no legitimate work” under the contracts, lawyers with the Justice Department’s criminal division wrote.

Mr. Cuellar “agreed to influence legislative activity and to advise and pressure high-ranking U.S. executive branch officials regarding measures beneficial to the bank,” prosecutors said.

Mr. Cuellar is one of the more conservative Democrats in the House and the only anti-abortion member of his party in the chamber. The charges are similar to the indictment brought against Senator Robert Menendez, a Democrat from New Jersey, who was charged with accepting bribes on behalf of Egyptian businesses.

In a statement before the indictment, Mr. Cuellar maintained his innocence and said he cleared his wife’s work with the Ethics Committee. He vowed to run and win re-election despite the charges.

“I want to be clear that both my wife and I are innocent of these allegations,” Mr. Cuellar said. “Everything I have done in Congress has been to serve the people of South Texas.”

“Before I took any action,” he added, “I proactively sought legal advice from the House Ethics Committee, who gave me more than one written opinion, along with an additional opinion from a national law firm.”

Mr. Cuellar said he tried to meet with federal prosecutors in Washington to explain his side of the story, but they declined the meeting.

The F.B.I. searched Mr. Cuellar’s Laredo home in 2022, but he won a close primary victory anyway over a more progressive challenger, Jessica Cisneros.

Representative Hakeem Jeffries of New York, the minority leader, said Mr. Cuellar would take leave from his post as the top Democrat on the Homeland Security Appropriations Subcommittee while he fights the charges.

“Henry Cuellar has admirably devoted his career to public service and is a valued member of the House Democratic Caucus,” said Christie Stephenson, a spokeswoman for Mr. Jeffries. “Like any American, Congressman Cuellar is entitled to his day in court and the presumption of innocence throughout the legal process.”