In a letter to Mr Garland last week, the senator accused the agency of carrying out a “politically-constrained and perhaps fake” investigation into Mr Kavanaugh ahead of his Senate confirmation, The Guardian first reported.
The FBI conducted the investigation after professor Christine Blasey Ford accused Mr Kavanaugh of sexually assaulting her in 1982 while they were both in high school.
Mr Kavanaugh also faced other allegations of misconduct after Ms Ford’s accusations of the alleged assault came to light.
Mr Kavanaugh has categorically denied all allegations.
At the time, Democrats criticised the narrow scope and time limitation of the FBI’s inquiry into the allegations and the number of witnesses, with neither Mr Kavanaugh or Ms Ford having spoken to the FBI.
Mr Whitehouse’s letter alleges that some witnesses who wanted to share their accounts with the agency “could find no one at the Bureau willing to accept their testimony.”
The letter claims that when “members made inquiries we faced the same experience: the FBI had assigned no person to accept or gather evidence.”
“This was unique behavior in my experience, as the Bureau is usually amenable to information and evidence,” Mr Whitehouse wrote.
He added: “But in this matter the shutters were closed, the drawbridge drawn up, and there was no point of entry by which members of the public or Congress could provide information to the FBI.”
The letter then criticises the use of a “tip line” as an entry point for “additional allegations and other potential corroborating evidence.”
The senator claims it appears that no review had been taken of information that flowed through the tip line and senators “could get no explanation of the tip line procedures.”
“This ‘tip line’ appears to have operated more like a garbage chute, with everything that came down the chute consigned without review to the figurative dumpster,” the letter says.
Mr Whitehouse goes on to criticise FBI director Christopher Wray for refusing to answer Congressional inquiries about the investigation.
“Senators’ questions for the record from that July 2019 oversight hearing remain unanswered today,” the senator writes, adding: “Such stonewalling does not inspire confidence in the integrity of the investigation.”
The lawmaker argues that if standard procedures were violated and the agency conducted a “fake” investigation, a congressional oversight would be required to “understand how, why, and at whose behest and with whose knowledge or connivance.”
“It cannot and should not be the policy of the FBI to not follow up on serious allegations of misconduct during background check investigations,” Mr Whitehouse concludes.
The Independent has contacted the FBI and the Department of Justice for comment.
Following the FBI’s investigation, Mr Kavanaugh was sworn in as a US Supreme Court justice, becoming the 114th person to serve on the court.
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