Congresswoman Alexandria Ocasio-Cortez, a rising star of the Democratic Party, admonished a Republican congressman who allegedly hurled a sexist slur at her on the steps of the US Capitol.

Ocasio-Cortez, 30, a progressive lawmaker from New York popularly known as "AOC," said Florida Representative Ted Yoho had "put his finger in my face."

"He called me disgusting, he called me crazy, he called me out of my mind," Ocasio-Cortez said during a nearly 10-minute speech on the floor of the House of Representatives.

"In front of reporters, Representative Yoho called me - and I quote - a 'fucking bitch,'" she said.

Ocasio-Cortez, the youngest member of Congress, said she was not looking for an apology from the 65-year-old Yoho - but that his behaviour was symptomatic of a wider problem of attitudes towards women.

"What we are seeing is that incidents like these are happening in a pattern," she said. "This is a pattern of an attitude towards women and dehumanisation of others."  

"All of us have had to deal with this in some form," she continued. "I have waited tables in restaurants. I have tossed men out of bars that have used language like Mr. Yoho's.

"This is not new and that is the problem," she said. "It is cultural.

"It is a culture of lack of impunity, of accepting of violence and violent language against women, an entire structure of power that supports that," the New York lawmaker said.

"Because not only have I been spoken to disrespectfully, particularly by members of the Republican Party," she said.

"But the president of the United States last year told me to go home to another country with the implication that I don't even belong in America."

Ocasio-Cortez is of Puerto Rican origin but was born and raised in New York City. 

Speaking on the House floor on Wednesday, Yoho apologised "for the abrupt manner of the conversation I had with my colleague from New York" but denied calling her an "offensive name."