Ralph Northam, the governor of the US state of Virginia, has vowed to remain in office despite widespread calls for his resignation after a racist photo surfaced in his yearbook page from more than 30 years ago.

Mr Northam said at a news conference that he had prematurely apologised for appearing in a picture of a person in blackface and another wearing a Ku Klux Klan outfit.

The photo appeared in his 1984 medical school yearbook.

The Democratic governor said on Saturday that he, in fact, was not in the photo and had never even seen the yearbook until Friday. “I am not in that photograph,” he told reporters gathered at the Executive Mansion in Richmond, calling the shot offensive and horrific.

Mr Northam disclosed that he once had used shoe polish to darken his face as part of a Michael Jackson costume he fashioned for a 1984 dance contest in Texas when he was in the US Army. He said he regretted that he did not understand “the harmful legacy of an action like that”.

His refusal to resign signals a potential bruising fight between Mr Northam and his former supporters.

Leaders in both parties have repeatedly urged Mr Northam to resign, saying he has lost the public’s trust.

Many leading politicians, including House Speaker Nancy Pelosi, had urged the governor to “do the right thing” after the photo emerged.

Late Term Abortion
Virginia governor Ralph Northam (Steve Helber/AP)

The calls for Mr Northam to step down came in a wave after the Democrat had initially apologised for appearing in a photo in which one person is dressed in blackface and another is wearing a full Ku Klux Klan uniform.

The yearbook images were first published on Friday by the conservative news outlet Big League Politics.

The Virginian-Pilot later obtained a copy from Eastern Virginia Medical School, which Mr Northam attended.

The photo shows two people looking at the camera, one in blackface wearing a hat, bow tie and plaid trousers; the other in a full Ku Klux Klan robe.

In his first apology, issued in a written statement, Mr Northam called the costume he wore “clearly racist and offensive”, but he did not say which one he had worn.

Governor Klan Blackface
Demonstrators hold signs and chant (Steve Helber/AP)

He later issued a video statement saying he was “deeply sorry” but was still committed to serving the “remainder of my term”.

“I accept responsibility for my past actions and I am ready to do the hard work of regaining your trust,” Mr Northam said.

Ms Pelosi called the photograph “racist and contrary to fundamental American values”.

She said on Saturday via Twitter that she is joining her colleagues in Virginia in calling for Mr Northam “to do the right thing” so that the people in Virginia can heal and move on.

Leading Democrats who are running for the party’s nomination for the 2020 presidential election added their voices to those calling for Mr Northam to quit.

Two African-American senators and would-be nominees, Cory Booker of New Jersey and Kamala Harris of California, joined the calls.

“These images arouse centuries of anger, anguish, and racist violence and they’ve eroded all confidence in Gov. Northam’s ability to lead,” Mr Booker said on Friday on Twitter.

“We should expect more from our elected officials. He should resign.”

Ms Harris said the “stain of racism should have no place in the halls of government.

“The Governor of Virginia should step aside so the public can heal and move forward together”.

Former US housing secretary Julian Castro, who has also entered the race, said: “This behaviour was racist and unconscionable. Governor Northam should resign.”