Patricia Roberts Harris angrily emphasized her sensitivity to problems of blacks and disadvantaged Americans yesterday during hearings on her nomination to head the Department of Housing and Urban Development.

The verbal wrangle erupted when Sen. William Proxmire, chairman of the Senate Banking, Housing and Urban Affairs Committee, suggested the department "needs someone sympathetic to the problems of the poor."

Harris, a member of the prestigious Washington law firm and former ambassador to Luxembourg, snapped back:

"You do not understand who I am. I am a black woman, the daughter of a Pullman car waiter. I am a black woman who even eight years ago could not buy a house in parts of the District. I didn't start out as a member of a prestigious law firm but as a woman who needed a scholarship to go to school. If you think I have forgotten that, you are wrong."

"It's not enough to be black or to be a woman or to be poor to have any particular kind of disability to understand the problems of so many people," said Proximire.

The Wisconsin Democrat said the last two HUD secretaries, James T. Lynn and Carla Hills, also were "brilliant lawyers" but were "amateurs" in the field of housing and "both were failures."

"HUD is in a shambles," Proximire said. He said it has neglected a major responsibility for publicly assisted housing construction for low-income families.

In 1968, Congress called for 600.000 publicly assisted housing starts a year. But, he said, in 19725 there were only 338,000, in 1973 234,000, in 1974 84,000, in 1975 56,000 and in 1976 "an incredible, pathetic" 41,000.

Again, on the subject of Harris' lack of specific experience in the field, Proximire said, "If I were hired to coach the Washington Redskins or the Green Bay Packers, the country would view it as an outrageous joke."

Proximire, who later said he was undecided whether to support or oppose her, predicted the Senate would confirm Harris, president-elect Jimmy Carter's only black Cabinet nominee.

Her nomination received enthusiastic support from other committee Democrats and Texas Sen. John Tower, the ranking Republican, who said he was "enormously impressed by Mrs. Harris' background and intelligence."

Proximire opened the hearing by criticizing Carter's failure to appoint someone to the housing post who had a background in housing and urban affairs.

"Do you have that kind of track record? Frankly I can't find it," he said.

But Proximire then told the nominee: "You are nevertheless going to be confirmed . . . overwhelmingly because anyone in the Senate these days who calls fro qualifications other than brains and character for Cabinet officers is regarded as somehow unrealistic, and you certainly have both brains and character."

Harris, in her opening statement and under questioning by the committee members, said she supports:

Public housing "so long as there is as disequilibrum between housing supply and housing demand."

The federal income tax deduction for mortgage interest payments.

Expansion of the urban homesteading program in which rundown center city housing is made available at practically no cost to persons who renovate it and live in it.