Amy Lappos said Mr Biden had touched her face with both hands and rubbed noses with her a decade ago.

The allegation comes after another women, Lucy Flores, said Mr Biden kissed her on the back of her head at a campaign event.

Mr Biden has said he did not believe he has ever acted inappropriately.

The former Delaware senator, who served as Barack Obama's vice-president in 2009-17, is seen as a possible frontrunner in the race for the Democratic presidential nomination.

What do his accusers say?

Ms Lappos, a 43-year-old former aide to a Democratic congressman, said Mr Biden touched her inappropriately at a fundraiser in a private home in Hartford, Connecticut, in 2009.

She told the Hartford Courant the then vice-president entered the kitchen to thank a group of aides, before wrapping both hands around Ms Lappos' face and pulling her in to rub noses with her.

Ms Lappos called on Mr Biden not to run for the White House, saying: "Uninvited affection is not okay. Objectifying women is not okay."

Ms Flores was running as the Democratic candidate for Nevada's lieutenant governor in 2014 when Mr Biden flew in to support her bid.

As she prepared to go on stage, Ms Flores say Mr Biden placed two hands on her shoulders from behind, smelled her hair then planted "a big slow kiss on the back of my head".

How has Mr Biden responded?

Asked about the new allegation, a spokesman for Mr Biden referred reporters to a statement he issued on Sunday.

"In my many years on the campaign trail and in public life, I have offered countless handshakes, hugs, expressions of affection, support and comfort. And not once - never - did I believe I acted inappropriately," it read.

"But we have arrived at an important time when women feel they can and should relate their experiences, and men should pay attention. And I will," he added.

On Monday a spokesman also accused "right wing trolls" of presenting harmless images of Mr Biden interacting with women as evidence of inappropriate touching.

What's been the reaction?

A number of candidates for the 2020 Democratic presidential nomination have backed Ms Flores.

Senator Elizabeth Warren said Mr Biden "needs to give an answer", and Senator Amy Klobuchar said that in politics "people raise issues and they have to address them".

Some supporters though have defended him. Cynthia Hogan, a former aide to the vice-president, told the New York Times that Mr Biden "treated us with respect and insisted that others do the same".

An ally of Mr Biden told CNN he was not reconsidering a run for the White House following the allegations but stressed he was yet to make a decision.

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