Federal prosecutors said Monday that they aren’t convinced claims U.S. Sen. Robert Menendez cavorted with underage hookers – widely seen as discredited – are false.

Lawyers for the New Jersey Democrat last week asked a federal judge to dismiss charges that the senator took bribes from a Florida eye doctor, Salomon Melgen, and in exchange used his power to do business and personal favors for him.

The defense said the case is bogus because it sprang from "easily disprovable" claims that Menendez slept with underage prostitutes while hosted by Melgen at a Dominican Republic villa.

Three women who made the prostitution allegations later recanted and said they were paid to level the charges. Neither Melgen nor Menendez was charged with soliciting underage prostitutes.

But in a motion Monday asking the judge to ignore the defense arguments, Justice Department lawyers say the hooker allegations "were not so easily disprovable as the defendants suggest."

Prosecutors used the defense claims to highlight previously undisclosed tidbits on Menendez's pursuit of younger woman.

The lawyers say their investigation resulted from "specific, corroborated allegations that defendants Menendez and Melgen had sex with underage prostitutes in the Dominican Republic."