Washington (CNN) As Brett Kavanaugh faces a sexual assault allegation that has rocked his nomination to be a Supreme Court justice, one Democrat on the Senate Judiciary Committee has emerged as an outspoken critic against how Republicans are handling the issue: Hawaii Sen. Mazie Hirono.

Hirono, alongside New York Democratic Sen. Kirsten Gilibrand, accepted a letter on Thursday signed by more than 1,000 alumni of the Holton-Arms School *in support of Christine Blasey Ford, who attended the school when she says Kavanaugh allegedly sexually assaulted her.

Hirono and other Democrats have called for an FBI investigation into the matter, but Republicans have continued to deny the request.

"Why isn't Judge Kavanaugh asking for an FBI investigation if (he has) nothing to hide?" Hirono asked during a news conference about the letter.

Ford's story was leaked to the press earlier this month before she came forward to the Washington Post. Her lawyer told CNN she's now receiving death threats over the allegation. Hirono said the threats, brought on by her outing, constitute being labeled as "intimidation of a witness."

"I call upon the FBI on their own to investigate this occurrence and all the threats she's undergoing," she added.

Hirono, one of just four women serving on the Senate Judiciary Committee -- the panel overseeing Kavanaugh's confirmation -- first brought up topic of sexual misconduct during Kavanaugh's confirmation hearing earlier this month.

She asked Kavanaugh, "Since you became a legal adult, have you ever made any unwanted requests for sexual favors or committed any verbal or physical harassment or assault of a sexual nature?" as well as "Have you ever faced discipline or entered into a settlement related to this kind of conduct?" Kavanaugh answered no to both questions.

The Hawaii senator told CNN's "New Day" on Wednesday that she asks these questions of every nominee who comes before the committees she sits on.

"I've asked this of ... I would say at this point about 100 nominees," she remarked.

After Hirono posed the questions to Kavanaugh, it emerged that Ford sent a letter to Congress prior to the hearings accusing him of physical and sexual assault, when they were both teenagers in the 1980s.

Ford alleges that at a party in high school, Kavanaugh pushed her into a bedroom along with his former classmate and that Kavanaugh attempted to remove her clothes. She also says Kavanaugh put his hand over her mouth when she attempted to scream. Kavanaugh said he "categorically and unequivocally" denies the allegation, which he called "completely false." Mark Judge, the other classmate identified in the allegation, also denied the incident occurred.

Following the public disclosure of the alleged incident, Hirono joined other Democrats demanding more than two witnesses at the Judiciary hearing and at a news conference on Tuesday. She has said she believes Ford.

Hirono also expressed her frustration at the broader issue -- sexual harassment and assault in general.

"Guess who is perpetuating all of these kinds of actions? It's the men in this country. And I just want to say to the men in this country: just shut up and step up, do the right thing for a change," she said at the news conference.

Despite the demands by Ford's legal team and Senate Democrats for an FBI investigation, Senate Judiciary Chairman Chuck Grassley and President Donald Trump have opposed holding an FBI investigation into the incident. Grassley has instead scheduled a hearing for next Monday for both Ford and Kavanaugh to testify about the incident.

Grassley, a Republican from Iowa, set a deadline of Friday at 10 a.m. ET for a decision from Ford on whether she will testify, and it's unclear whether she'll choose to appear.

Hirono said Wednesday on CNN's "New Day" that committee is setting up a situation "where there is not even a modicum of fairness extended" to Ford without a proper FBI investigation into the incident.

"I think we should all be focused on why the heck does she not want to come. She doesn't want to be a part of a railroad job," Hirono said. She asserted that Republicans are rushing to confirm Kavanaugh because the court's "session is going to start in October and the President wants his guy there to, he hopes, help him evade criminal or civil proceedings."

Hirono also railed against Grassley's assertion that Republicans have done all they can do to contact Ford and have her appear before his committee, telling ABC's "World News Tonight" on Wednesday that "That's such bulls*** I can hardly stand it."

This story has been updated to include additional developments.