Sen. Tom Cotton (R-Ark.) said Monday morning that he is putting a hold on three of President Obama’s ambassadorial nominees until the administration shows it is taking steps to punish Secret Service staff involved in leaking unflattering information about a lawmaker.

“This was apparently a violation of law, and absolutely shocking conduct,” Cotton said in an interview. “The executive branch all the way up to the West Wing needs to treat this with the seriousness it requires.”

Cotton called on Homeland Security Secretary Jeh Johnson to “personally attend” to disciplining top Secret Service leaders — specifically including new Director Joseph Clancy — for the leak of personnel information about of Rep. Jason Chaffetz (R-Utah) from the agency’s files.

Cotton also called on the Department of Justice to conduct a criminal investigation into the matter, which involves Secret Service agents repeatedly accessing and sharing a file showing that Chaffetz had been rejected for a job as a Secret Service agent a decade ago. Accessing and sharing such personnel information, with rare exceptions, is a violation of federal privacy law.

The senator’s hold applies to three nominees who have been waiting for months for the Senate to confirm them — Cassandra Butts, for ambassador to Bahamas; Azita Raji, ambassador to Sweden; and Samuel Heins, ambassador to Norway.

Cotton said he will consider blocking more nominees if the administration refuses to fully investigate and discipline Secret Service staff.

“When President Obama and Secretary Johnson take appropriate action, I will likewise take action and release these and future objections,” Cotton said.

The senator is among a growing group of lawmakers in both parties expressing outrage about how the Chaffetz information was handled. Chaffetz, chairman of the House Oversight and Government Reform Committee, has been a vocal critic of the Service.

An investigation by a top federal watchdog found that 45 Secret Service employees improperly accessed Chaffetz’s file in an agency database following a contentious hearing Chaffetz ran in March, and that an assistant director of the agency urged making the information public. It was published two days later in the Daily Beast and Washington Post.

Cotton said Clancy and 18 other senior supervisors are culpable because they were aware of the information being circulated within the agency and should have known it was a privacy violation but did nothing to stop it or prevent the material from being leaked. Cotton said the administration needs to reconsider whether Clancy is the right person for the job of reforming the troubled Secret Service.

Cotton said he finds it very troubling that Clancy acknowledged last week that he needed to revise his account of his role in the matter. Clancy initially told investigators with the Department of Homeland Security’s Office of Inspector General in July that he didn’t know anything about his staff circulating the Chaffetz information until it was about to be published in April. Just before the report’s release last week, Clancy notified Inspector General John Roth that he had recalled learning from a top deputy that the information was circulating among his staff but considered it a “speculative” rumor.

“How could this happen?” Cotton asked. “How could someone hired to change the culture of his agency be so indifferent to potential illegal activity and to such a constitutional affront to the legislature that he did nothing? Absolutely nothing until the press broke the story.”

Cotton said a full criminal investigation should look at Clancy’s shifting account, which was first reported by The Post.

“If he intentionally misled investigators, he has to be fired,” Cotton said. “But even if he didn’t mislead anyone, his conduct is not what we would want or expect from the person in charge of reforming this agency.”

The White House declined to comment Monday, but in a news briefing last week, White House spokesman Josh Earnest said the president takes the leak of the private information very seriously. Earnest said the personal apologies extended to Chaffetz by Clancy and Johnson show the gravity with which the administration is handling the matter.

“It certainly is not routine for the director of the Secret Service to personally call someone to offer an apology for the conduct of his agency. It certainly is extraordinary for the secretary of Homeland Security to place the same telephone call,” Earnest told reporters. “I think that should be a pretty clear indication to you just how seriously the administration takes this matter, and how seriously the Secret Service takes their responsibility to live up to the high standards that they’ve set for themselves at that agency.”