A second woman has come forward with allegations of sexual misconduct against Brett Kavanaugh, US President Donald Trump's embattled nominee for the Supreme Court.

Senate Democrats are investigating the bombshell claim by Deborah Ramirez, according to the New Yorker magazine.

The 53-year-old says Mr Kavanaugh exposed himself to her during a college party at Yale University in the 1980s, thrust his genitals in her face and caused her to touch them without her consent.

Mr Kavanaugh denied the incident occurred, calling it "a smear, plain and simple".

"The people who knew me then know that this did not happen, and have said so," the conservative judge said in a statement.

Meanwhile, Mr Trump has defended his Supreme Court nominee.

Speaking after he arrived in New York to attend the UN General Assembly, the US President said: "Judge Kavanaugh is an outstanding person. I am with him all the way."

The allegation is the latest twist in Mr Kavanaugh's already heated confirmation battle.

He is set for a dramatic hearing this week involving a university professor who recently came forward accusing him of assaulting her when they were in high school.

"I look forward to testifying on Thursday about the truth, and defending my good name - and the reputation for character and integrity I have spent a lifetime building - against these last-minute allegations," Mr Kavanaugh said.

The New Yorker article was co-written by Ronan Farrow, whose reportage around disgraced movie mogul Harvey Weinstein was key in opening the floodgates of the #MeToo movement, along with another reporter Jane Mayer.

At least four Democratic senators have received information about Ms Ramirez's allegation, the magazine said, of whom at least two have begun investigating it.

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Senior Republican staffers have likewise learned of the allegation and expressed concern about its impact on the nomination, The New Yorker added.

"This is another serious, credible, and disturbing allegation against Brett Kavanaugh. It should be fully investigated," Senator Mazie Hirono, of Hawaii, was quoted as saying.

When The New Yorker first contacted Ms Ramirez, it said she was reluctant to come forward, partly because of gaps in her memory because she had been drinking at the time of the incident.

But having spent six days assessing her memories and consulting her attorney, she felt more confident and was now calling for an FBI investigation.

"I would think an FBI investigation would be warranted," she told The New Yorker.

The magazine said it had not found eyewitnesses to confirm that Mr Kavanaugh was at the party.

However, one former classmate remembered hearing about the incident from another, and independently corroborated many of the details offered by Ms Ramirez.