Hours after Rep. Raul Grijalva (D-AZ) penned an op-ed calling for Ryan Zinke’s resignation, the interior secretary hit back by calling the top Democrat a “drunk.”

“It’s hard for him to think straight from the bottom of the bottle,” Zinke tweeted on Friday. “This is coming from a man who used nearly $50,000 in tax dollars as hush money to cover up his drunken and hostile behavior.”

The Trump cabinet official continued: “He should resign and pay back the taxpayer for the hush money and the tens of thousands of dollars he forced my department to spend investigating unfounded allegations.”

The Arizona congressman, who will likely chair the House Natural Resources Committee, which oversees Zinke’s agency, said in a USA Today op-ed on Friday morning that Zinke should step down because of his multiple “ethical and managerial failings.”

“While the secretary continues to project confidence, questions have grown since the election about his future plans, and the White House reportedly fears that he would be unable to withstand scrutiny on Capitol Hill,” Grijalva wrote. “Those fears are justified. Mr. Zinke has never even tried to offer an explanation for the sheer scope of his well-documented scandals.”

Zinke’s allegations mirror a report by the Washington Times claiming that in 2015 the Arizona congressman pushed a severance package on a former employee who complained of Grijalva’s alleged frequent drunkenness and hostile work environment—allegations the lawmaker vehemently denies.

“Last week, the Washington Times contacted me seeking comment on what it described as a sexual harassment claim that, in fact, had never been made,” Grijalva said in a statement regarding the employee’s legal threats. “Once the paper realized its original story was provably false, staff regrouped over the holidays and decided to run a misleading article trying to link me to sexual harassment complaints made against other people.”

Grijalva responded to Zinke's hit on Friday, writing on Twitter that instead of addressing the "credible and serious" allegations against him, the interior secretary resorted to "personal attacks."

As the Democratic ranking committee member, Grijalva has led multiple ethical inquiries into Zinke, including requesting the inspector general’s office to look into reports that the secretary entered into a real-estate deal with the chairman of oil-services company Halliburton. Last month, the IG referred that investigation to the Department of Justice.

“Should I chair the committee in January, as I hope to do, those questions will only intensify as part of my and my colleagues’ legitimate oversight duties. If Mr. Zinke stays, stonewalling in the belief that a cabinet secretary answers only to Trump would be a mistake,” Grijalva said.

To date, Zinke has been targeted in 18 ethical probes since joining the Trump administration last year.

“The important thing to us was that Mr. Zinke not be allowed to treat his office as a source of personal enrichment. The fact that the Justice Department was alerted is Mr. Zinke’s fault, not the fault of the media or anyone else his office has chosen to blame,” Grijalva wrote.

Zinke has categorically denied all allegations of ethical misconduct—the tally now exceeding all the allegations made against his four predecessors.

In an interview on Thursday evening with Fox News @ Night host Shannon Bream, Zinke claiming he is “10 for 10” in being cleared of these “politically motivated” investigations, adding he will probably be investigated next for saying “Merry Christmas.”

“I’ve been investigated on my socks. I have been investigated taking jets, which I don’t, completed,” he said. “I’ve had 10 investigations completed, and you know what they all say? Ryan Zinke follows all the rules, all the regulations, all the procedures.”

When the host concluded the interview, saying she did not have time for a holiday-related question, Zinke shot back: “Well, I’ll say it first. Merry Christmas. If I should be investigated by saying it, what—Merry Christmas, America.”

Despite his denials, Zinke’s tenure in the Trump administration reportedly remains tenuous, as multiple outlets claimed last month that the president intends to replace a number of cabinet secretaries.

The mounting ethical violations and the potential DOJ investigation originating with Grijalva haven’t seemed to sway Trump, however, as the president publicly stood up for his interior secretary last month, telling reporters Zinke has “done a good job.”

“I think he’s done a very good job. I do think he’s done a very good job,” Trump told reporters before boarding Air Force One on the eve of the midterm elections.