NEW YORK — Federal prosecutors accused Sen. Bob Menendez on Thursday of secretly acting as an agent of the government of Egypt while serving as the chair of the Senate Foreign Relations Committee, adding to the slate of criminal charges for which the New Jersey Democrat was indicted last month.

Prosecutors in the Manhattan U.S. attorney’s office unveiled an updated indictment adding the charge of conspiracy for a public official to act as a foreign agent, alleging that Menendez; his wife, Nadine Menendez; and a New Jersey businessman, Wael Hana, used his Senate position to benefit the government of Egypt without registering as foreign agents.

The new indictment comes three weeks after a federal grand jury charged all three — along with two other New Jersey businessmen — with conspiracy to commit bribery, conspiracy to commit honest services fraud and conspiracy to commit extortion. Prosecutors accused the Menendezes of accepting hundreds of thousands of dollars in bribes in cash, gold bars, a Mercedes-Benz C-300 convertible and home mortgage payments in exchange for using the senator’s position to benefit the businesspeople and the government of Egypt between 2018 and 2022.

All of the defendants pleaded not guilty to the charges in the original indictment.