People working for Democratic senators are overwhelmingly white and mostly women, according to a first-of-its-kind report on diversity in some congressional offices.

The current Congress is the most diverse in history, with more minority lawmakers than ever before and a record 21 women in the Senate. But a cadre of current and former congressional staffers, lobbyists and party donors have been pressuring congressional leaders — especially Democrats — to intensify the search for minorities to fill jobs on Capitol Hill and in district offices nationwide.

Responding to the pressure, Senate Minority Leader Charles E. Schumer (D-N.Y.) released a report Friday that confirms what staffers and outside observers have long believed: Despite having 16 women in the caucus and more minority senators than ever, Democratic Senate staffing is overwhelmingly white.

Thirty-two percent of staffers are “non-Caucasian,” defined as African American, Asian/Pacific Islander, Latino, Native American or Middle Eastern/North African, according to the report. Fifty-four percent of staffers are women, 46 percent are men.

The report “confirms what we’ve all known for some time — that there is a significant diversity problem that cannot be allowed to continue in the most representative branch of our government,” said Don Bell, director of the Black Talent Initiative at the Joint Center for Political and Economic Studies, a group that has been studying congressional staffing issues for years. He called on other House and Senate leaders “to follow suit and begin collecting this vital information.”

Across the Senate Democratic staff, 13 percent are African American, roughly on par with the national percentage; 10 percent are Latino, behind the roughly 17 percent nationally; 8 percent are Asian-Pacific, ahead of the national percentage; 4 percent are Native American; and 3 percent are Middle Eastern/North African. (Some staffers chose more than one category.)

“As we continue the full-court press to make the Senate a more diverse place, this survey will be important to help us track our progress,” Schumer said in a statement announcing the report’s release. “The more diverse the Senate is, the better it can serve our diverse country.”

House and Senate Republicans do not publicly report data on staffing gender and ethnicity and declined requests in the past when asked by The Washington Post. House Minority Leader Nancy Pelosi (D-Calif.) also has intensified her caucus’s push to hire more minorities, and a committee of Democratic lawmakers is considering options similar to what Schumer has adopted.

Schumer’s report mirrors similar surveys conducted by the Office of Personnel Management for executive branch employees that ask workers to self-report gender, ethnicity and other characteristics. About 94 percent of the roughly 2,800 people who work for Democratic senators responded to the survey, according to Schumer’s office.

The report “is a major step in the right direction, but we have a lot of work to do,” said Darrel Thompson, a former deputy chief of staff to former Senate majority leader Harry M. Reid (D-Nev.), who is now with The Group, a government relations firm. Thompson helped Reid establish the Senate Democratic diversity office that helps recruit and place minority job applicants.

Among individual Democratic senators, the staff of Brian Schatz (Hawaii) ranks the most diverse, with 66 percent of his employees identifying as minority, most of them as Asian or Pacific Islander, the report said. Sens. Kamala D. Harris (Calif.) and Mazie Hirono (Hawaii) rank second at 61 percent, followed by Sens. Cory Booker (N.J.) at 57 percent, Chris Van Hollen (Md.) at 54 percent and Tom Udall (N.M.) at 52 percent.

Cristina Antelo, a principal at the Podesta Group and former Democratic Senate staffer and current vice chairman of the nonpartisan Congressional Hispanic Caucus Institute, noted that 43 percent of Udall’s staff is Latino, the most of any senator, probably because his chief of staff, Bianca Ortiz-Wertheim, is one of only two Hispanic women holding that role in the Senate.

“When you have someone like that in a position like chief of staff, it makes a difference,” she said.

On the flip side, Sen. Jon Tester (Mont.) has the least diverse staff at 7 percent, followed by Sens. Joe Manchin III (D-W.Va.) at 9 percent and Heidi Heitkamp (N.D.) at 10 percent. All three Democrats represent overwhelmingly rural and white states.

Overall, “there are a bunch of offices who have numbers that are reflective of their states that I’m actually happy to see,” Antelo said.

Francisco Bencosme, president of the Congressional Hispanic Staff Association and a Senate Foreign Relations Committee staffer, called Schumer’s decision to release the report “significant” because it helps establish a marker for future years. He said his group will be working with offices that have low percentages of minority workers to help identify job candidates.

On gender, Sens. Michael F. Bennet (Colo.) and Bill Nelson (Fla.) employ the most women, with 66 percent each. The Democratic female senator with the highest percentage of female employees is Sen. Jeanne Shaheen (N.H.) at 65 percent. Sen. Robert Menendez (N.J.) employs the highest percentage of men at 60 percent.

The report also accounts for the diversity of professional committee staffs. One hundred percent of Democratic staffers on the Indian Affairs Committee are minority, — 60 percent are Native Americans, the report said. Staffs for the committees on Appropriations (5 percent), Agriculture (7 percent) and Banking (8 percent) are the least diverse.

“I think the committees have some work to do,” Antelo said, adding that it’s “concerning” that several committees lack any Asian, African American or Latino staffers.

Schumer agreed to compile the data earlier this year after meeting with leaders of Asian, African American and Latino congressional staffing associations. He also agreed to expand the diversity office and asked Democratic senators to adopt the “Rooney Rule,” an NFL hiring practice that requires pro football teams to interview at least one minority applicant for head coaching and other senior team positions. In the case of senators, Schumer asked that at least one minority applicant be interviewed for every staff opening. Pelosi recently asked House Democrats to adopt the same policy.

Some Democratic staffers expressed surprise Friday that Schumer opted to publish the report, but its publication — and that it was conducted at all — follows several years of pressure from Asian and Latino congressional staff associations. In recent years, lobbyists and Democratic donors who are Asian, African American and Latino have pressured Schumer, Pelosi and other party leaders to increase minority hiring and publicly release the numbers to hold lawmakers to account.

The issue earned wider attention when minority staffers began circulating New York Daily News columns by civil rights activist and writer Shaun King, who used essays to call out Democrats for failing to promote minorities to senior positions.

“Democrats in the Senate have their own problems with bigotry,” King wrote in January, noting that the only two black chiefs of staff worked for Republican senators, Tim Scott (S.C.), who is black, and Jerry Moran (Kan.). Jonathan Burks, chief of staff to House Speaker Paul D. Ryan (R-Wis.), is also black.