WASHINGTON (Reuters) - The U.S. Senate Select Committee on Ethics said on Thursday that Senator Robert Menendez violated congressional rules by “knowingly and repeatedly” accepting impermissible gifts over a six-year period and must repay their fair market value.

FILE PHOTO: Senator Robert Menendez (D-NJ) waits to question Jerome Powell on his nomination to become chairman of the U.S. Federal Reserve during a hearing before the Senate Banking, Housing and Urban Affairs Committee in Washington, U.S., November 28, 2017. REUTERS/Joshua Roberts

Menendez, a Democrat from New Jersey, was indicted several years ago on criminal corruption charges related to the gifts that he received from Dr. Salomon Melgen, a Florida eye doctor who was convicted of Medicare fraud earlier this year.

Menendez’s trial ended with a hung jury late last year and Justice Department prosecutors subsequently asked the judge to dismiss the charges against him.

Despite the court outcome, the Ethics Committee, made up of three Republican senators and three Democratic senators, found that he violated Senate rules.

“The Committee has found that over a six-year period you knowingly and repeatedly accepted gifts of significant value from Dr. Melgen,” the committee wrote in a letter to Menendez released on Thursday.

Melgen paid for Menendez to take private and commercial flights, and stay at a luxury hotel in Paris and at a villa in the Dominican Republic, the committee said.

During the same period, Menendez used his status as a senator to help Melgen, including by intervening after the Centers for Medicare and Medicaid Services found that Melgen had overbilled them by $8.9 million, the committee said.

“The Committee concludes that your actions violated Senate Rules and related statutes, and reflected discredit upon the Senate,” it continued, saying Menendez was “severely admonished” for his actions.

Menendez’s office did not immediately respond to a request for comment.

The committee began its review of Menendez in 2012 but paused it during the criminal probe, as is custom. The committee’s review resumed in November 2017 once the criminal charges against Menendez were dismissed.

After an initial period of review, the committee typically decides whether to dismiss the matter entirely, or determines there was evidence of rules violations that were inadvertent or minor. If there is evidence, the committee can still decide to dismiss the matter, or issue a public letter of admonition, such as the one received by Menendez.

If the committee decides there is enough evidence to begin what it calls an adjudicatory review, it can lead to a formal investigation and trial resulting in more serious punishments such as censure or expulsion. Such punishment is rare and no U.S. senator has been expelled since the U.S. Civil War in the 1860s.