An angry Democratic Sen. Bob Menendez on Wednesday fired back at his Republican opponent for airing a new ad reviving salacious allegations that the senator had sex with underage prostitutes during past trips to the Dominican Republic -- calling the claims "lies."

“I’m going to keep my remarks brief because I’m worried about what language I might use,” a fired-up Menendez said at a Hackensack news conference, surrounded by female supporters.

The New Jersey senator called the ad from Republican opponent Bob Hugin “despicable” and “desperate.”

“These are lies,” Menendez said. “I know it. You know it. And Bob Hugin damn sure knows it as well.”

Menendez has long denied the allegations as a smear since they first surfaced on a news site in 2012.

“It stoops so low with its bogus lies that it might as well been directed by Donald Trump himself,” the Democratic senator said.

Menendez’s press conference came after Hugin, a wealthy pharmaceutical executive, began airing the explosive television ad this week that cites papers filed in federal court by prosecutors in 2015 acknowledging the FBI probed the prostitution allegations as part of its corruption case against Menendez.

“It’s right here in this shocking FBI affidavit,” the ad’s narrator says. “President Obama’s Justice Department had evidence that for several years, Senator Menendez had been traveling to the Dominican Republic to engage in sexual activity with prostitutes – some of whom were minors.”

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Prosecutors declined to bring charges related to the prostitution claims, though they did pursue a bribery case against him. A mistrial was declared last year after the jury failed to reach a verdict in that case.

In 2015 court papers, prosecutors said the FBI investigated Menendez and donor Salomon Melgen after being presented “with specific, corroborated allegations” they had sex with underage prostitutes, though they decided against bringing any charges on those claims. (Melgen was later convicted in a separate Medicare fraud case, and sentenced to 17 years in prison.)

“Presented with specific, corroborated allegations that defendants Menendez and Melgen had sex with underage prostitutes in the Dominican Republic, the Government responsibly and dutifully investigated those serious allegations,” the papers stated, in response to claims from the defendants that the allegations were "false" and tainted the case.

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The prosecutors also wrote: “Confronted with corroborating evidence of such serious crimes, it would have been an inexcusable abdication of responsibility not to investigate these allegations.”

The Hugin ad’s narrator also takes a swing at Menendez over claims made at the time by Menendez’s lawyers, as documented in the 2015 court filing, who argued “such easily disprovable” allegations of cavorting with underage prostitutes “would hardly be a federal crime even had it been true.”

“As an initial matter, it is most certainly a federal crime to leave the country for the purpose of engaging in a commercial sex act with a minor, and the defendants’ suggestion to the contrary is unsettling,” prosecutors wrote in response.

New Jersey hasn’t elected a Republican to the Senate in 46 years. But Hugin has been spending millions on negative ads reminding voters of Menendez’s past ethics troubles.

A sign that Democrats are taking Hugin’s challenge seriously: the Senate Majority PAC, which is aligned with Senate Democratic Leader Chuck Schumer, announced plans to spend $3 million this week on anti-Hugin ads.