The senior FBI official leading the investigation in Florida of the attempted assassination of former President Donald Trump expressed rabid hatred of Mr. Trump and retaliated against FBI personnel who supported the former president, whistleblowers say.

Jeffrey Veltri, special agent in charge, was ordered by superiors to scrub his social media accounts of anti-Trump vitriol before he was promoted last year to head the Miami field office, an FBI whistleblower reported to Congress last year.

Mr. Veltri is now leading the FBI’s investigation into Sunday’s assassination attempt on Mr. Trump, the second in two months.

The FBI denies asking Mr. Veltri to erase social media posts.

His role in the case, however, raised concerns among those who say the federal government is failing to adequately protect the former president or provide transparency about the security lapses that put Mr. Trump’s life at risk.

Tom Fitton, president of the conservative watchdog Judicial Watch, wrote on X: “CONFLICT OF INTEREST: The Biden-Harris FBI, which is right now trying to jail Trump, is investigating two attempts on his life.”

The former president was playing at the Trump International Golf Course in West Palm Beach when Secret Service agents spotted the muzzle of a rifle poking through the tree line. Agents fired at Ryan Routh, 58, who fled the scene without shooting. Mr. Routh was able to position himself within a few hundred yards of the sixth hole and hide there undetected for 12 hours, the FBI said.

Mr. Routh has been charged with two federal firearms violations and faces additional charges, including attempted assassination of the former president.

When he updated reporters on the case Monday, Mr. Veltri did not mention his sentiment of the former president.

“We view this as extremely serious and are determined to provide answers as to what led up to the events that took place,” Mr. Veltri said.

Whistleblowers tell a different story.

Tristan Leavitt, an FBI whistleblower attorney and president of the nonprofit watchdog group Empower Oversight, said Mr. Veltri was deputy assistant director of the FBI’s security division when “the so-called ‘Trump Questionnaire’ was used.”

“His bias against conservatives and those of his deputy, Dena Perkins, permeated the unit,” Mr. Leavitt wrote recently on X.

Whistleblower disclosures sent to the Justice Department’s office of the inspector general said the questionnaire asked about employees’ political and personal beliefs.

In a statement to The Times, the FBI said the agency has “full confidence in [Mr.] Veltri’s leadership of the Miami Field Office and the investigation of the attempted assassination of former President Trump.”

“This investigation is of the highest priority of the FBI. We are working closely with our partners and have hundreds of personnel from FBI Headquarters, Quantico, and multiple field offices supporting these efforts. All of us in the FBI are committed to conducting this investigation by the book, following the facts where they lead,” the statement said.

The FBI added, “No one in the FBI, to include the director and deputy director, ever asked Mr. Veltri to remove content from social media.”

Florida Gov. Ron DeSantis, a Republican, announced Tuesday that his top prosecutor, Attorney General Ashley Moody, will lead an independent investigation into the assassination attempt and will pursue attempted murder charges against Mr. Routh.

Mr. DeSantis said federal officials shouldn’t be left exclusively to investigate the matter because they are simultaneously prosecuting Mr. Trump in two cases, one in the Southern District of Florida, where he is facing felony charges for storing classified documents at his Mar-a-Lago estate.

Federal officials may also try to cover up their lapses that allowed two armed assassins in two months to get within several hundred yards of Mr. Trump, he said.

“Do we honestly think this agency, these agencies, are the best to turn around and do this investigation on a potential assassin, that some of them may or may not want to be held accountable for if there was something they could have done better with security?” Mr. DeSantis said. “I don’t think anyone can honestly claim that the federal government has been forthright and transparent about its past investigations. That’s just the reality. That’s just how these guys operate.”

Mr. Veltri’s involvement raises additional questions about transparency.

As The Times exclusively reported last year, an FBI whistleblower described Mr. Veltri as “adamantly and vocally anti-Trump” and said FBI Director Christopher A. Wray, Deputy Director Paul Abbate and then-Executive Assistant Director Jennifer Moore were involved in directing Mr. Veltri to scrub his social media accounts.

“The home of President Donald Trump is located in the area of responsibility of the Miami Field Office. It was well known that Veltri was adamantly and vocally Anti-Trump,” the whistleblower said in a disclosure to Congress obtained by The Times.

“Wray, Abbate and Moore wanted to ensure that Veltri appeared nonpolitical. Veltri was ordered to remove all of his Facebook and Social media posts that were Anti-Trump,” the whistleblower said.

The whistleblower said the bureau leaders weren’t concerned about Mr. Veltri’s “bias against Trump” but whether “information related to Veltri’s political bias can be removed from the public domain.”

Mr. Veltri, who before his promotion served as acting deputy assistant director of the bureau’s security division, also oversaw efforts to suspend the security clearances of an agent who seemed to be a “right-wing radical,” according to the disclosure.

The FBI said the whistleblower’s allegations about Mr. Veltri were false.

The FBI said Mr. Veltri was “selected through a competitive process to lead the Miami field office and is charged with carrying out the FBI mission in a fair and unbiased manner.”

The bureau added, “The reported allegations about political bias impacting decisions, the targeting of former military employees, and [Mr.] Veltri’s social media accounts and posts are demonstrably false.”

The FBI announced Mr. Veltri’s promotion to head of the Miami field office in March 2023, less than a year after the bureau raided Mr. Trump’s Mar-a-Lago estate in Palm Beach, Florida, looking for classified documents.

Mr. Veltri first came under congressional scrutiny after whistleblowers from the FBI’s security division said bureau officials were trying to purge agents with conservative political views who are “radical” or “disloyal” to the U.S.

Suspect behavior included refusing COVID-19 vaccinations and participating in religious activities.

In another whistleblower disclosure, Mr. Veltri and Dena Perkins, assistant section chief of the security division, were accused of trying to sideline agents, including military veterans, by stripping th