A second allegation of sexual misconduct has emerged against US Supreme Court nominee Judge Brett Kavanaugh.

The new accusation in a report from The New Yorker came just hours after negotiators had reached an agreement to hold an extraordinary public hearing on Thursday for Mr Kavanaugh and Christine Blasey Ford, who accuses him of sexually assaulting her at a party when they were teenagers.

Mr Kavanaugh denies the claim.

Presidential adviser Kellyanne Conway told CBS that the accusations against Mr Kavanaugh sound like “a vast left-wing conspiracy”, using rhetoric that echoed Hillary Clinton’s 1998 description of allegations that her husband, President Bill Clinton, had had affairs.

President Donald Trump was told about the New Yorker allegations hours before the piece’s explosive publication, according to a White House official.

Mr Trump cast doubt on the veracity and the timing of the piece, believing it was further proof of what he has been saying privately for days: that the Democrats and media were conspiring to undermine his pick.

The second claim against Mr Kavanaugh dates to the 1983-84 academic year, which was his first at Yale University.

Deborah Ramirez described the alleged incident after being contacted by The New Yorker magazine.

She alleges that Mr Kavanaugh exposed himself at a drunken dormitory party.

In a statement provided by the White House, Mr Kavanaugh said the event “did not happen” and that the allegation was “a smear, plain and simple”.

A White House spokeswoman added in a second statement that the allegation was “designed to tear down a good man”.

Senator Dianne Feinstein, the ranking Democrat on the Judiciary Committee, called for the “immediate postponement” of any further action on Mr Kavanaugh’s nomination.

Republicans on the Senate Judiciary Committee said they would investigate Ms Ramirez’s accusation.

Judiciary spokesman Taylor Foy complained that Democrats “actively withheld information” from the Republicans.

He said they appear “more interested in a political takedown” than a bipartisan process.

The New Yorker said it contacted Ms Ramirez after learning of a possible involvement in an incident with Mr Kavanaugh.

It said the allegation came to the attention of Democratic senators through a civil rights lawyer. The Democrats then began investigating.

Ms Ramirez was reluctant at first to speak publicly “partly because her memories contained gaps because she had been drinking at the time of the alleged incident”, The New Yorker reported.

After “six days of carefully assessing her memories and consulting with her attorney, Ramirez said that she felt confident enough of her recollections” to speak publicly, the report said.

Michael Avenatti, the lawyer representing porn actress Stormy Daniels in her legal fight with Mr Trump, claimed to represent a woman with information about high school-era parties attended by Mr Kavanaugh and urged the Senate to investigate.

Mr Avenatti said he will disclose his client’s identity in the coming days and that she is prepared to give evidence before the committee, as well as provide names of corroborating witnesses.

The accusation from Ms Ramirez raises the stakes further for a dramatic showdown on Thursday, as Mr Kavanaugh and Ms Ford give evidence in public about an incident she characterises as attempted rape – and that he says simply never happened.

Mr Kavanaugh’s nomination hangs precariously, with a handful of senators in both parties undecided on his nomination.

Defections among Republicans would probably block his path to the Supreme Court.

The White House is approaching Ms Ford’s potential testimony with trepidation, nervous that an emotional performance might not just damage Mr Kavanaugh’s chances but could further energise female voters to turn out against Republicans in November.

Still, the White House and Republicans have cast doubt on Ms Ford’s allegations.

The judiciary panel said it had talked to three other people who Ms Ford has told The Washington Post were at the party where the alleged assault took place – Mark Judge, Patrick J Smyth and Leland Ingham Keyser.

All three told investigators that they had no recollection of the evening in question, the committee said.

The Post reported that Ms Keyser said she still believes Ms Ford, even if she does not remember the party.

As he builds a case for his innocence, Mr Kavanaugh plans to turn over to the committee calendars from the summer of 1982.

Those calendars, he says, do not show a party consistent with Ms Ford’s description of the gathering in which she says he attacked her, The New York Times reported.

The calendars list basketball games, film outings, football workouts, college interviews and a few parties with names of friends other than those identified by Ms Ford, according to the Times.