A progressive Bay Area member of the U.S. House says fellow Sen. Dianne Feinstein, California Democrat, should resign immediately.

Rep. Ro Khanna, a member of the Congressional Progressive Caucus, said Ms. Feinstein, who will turn 90 in June and is Congress’ oldest member, can no longer function as an effective senator.

“It’s time for @SenFeinstein to resign. We need to put the country ahead of personal loyalty. While she has had a lifetime of public service, it is obvious she can no longer fulfill her duties,” Mr. Khanna said Wednesday.

He is the first sitting member of Congress to publicly say Ms. Feinstein, whose health issues have prevented her from voting in the Senate since Feb. 16, should resign and allow Democratic Gov. Gavin Newsom to appoint an interim senator.

Ms. Feinstein already had announced that she will not run for re-election in 2024, but she will remain in office for another 21 months.

“Not speaking out undermines our credibility as elected representatives of the people,” Mr. Khanna said.

His call was quickly seconded by another Democratic House member, albeit not one from California.

“I agree with @RoKhanna. Senator Feinstein is a remarkable American whose contributions to our country are immeasurable. But I believe it’s now a dereliction of duty to remain in the Senate and a dereliction of duty for those who agree to remain quiet,” said Rep. Dean Phillips, Minnesota Democrat.

Former House Speaker Nancy Pelosi smelled sexism though, saying that Ms. Feinstein “deserves the respect to get well and be back on duty.”

“I’ve never seen them go after a man who was sick in the Senate in that way,” Mrs. Pelosi said..