Donald Trump’s campaign has included on its list of delegates a self-proclaimed white nationalist who attempted to revoke the citizenships of all non-whites, including those with “more than one-eighth of Middle Eastern or Semitic blood.”

William Johnson, the national chairman of the far-right American Freedom Party, was one of 169 California delegates entered by the presumptive Republican presidential nominee’s campaign, authorities revealed on Monday.

Tim Clark, the director of the candidate’s California campaign, released a statement on Tuesday explaining that his team had made a mistake, saying: “Upon careful review of computer records, the inclusion of a potential delegate that had previously been rejected and removed from the campaign’s list in February 2016 was discovered.

“This was immediately corrected and a final list, which does not include this individual, was submitted for certification.”

However, a spokesperson for the California Secretary of State told ABC News that “the Trump campaign did not reach out to our office about removing William Johnson's name as a delegate until today [Tuesday, May 10] - which is past the statutory deadline to submit delegate lists to the Secretary of State's office.”

In 1985, Mr Johnson wrote a book called ‘Pace Amendment’ under the pseudonym James O Pace, in which he proposed a constitutional amendment to deport almost all non-white US citizens.

He told readers: “No person shall be a citizen of the United States unless he is a non-Hispanic white of the European race, in whom there is no ascertainable trace of Negro blood, nor more than one-eighth Mongolian, Asian, Asia Minor, Middle Eastern, Semitic, Near Eastern, American Indian, Malay or other non-European or non-white blood”.

His organisation, the American Freedom Party, features the headline “Philip Green, Jewish Criminality, and the Cost of Economic Parasitism” on its homepage.

It is described by the Southern Poverty Law Centre (SPLC) - a non-profit which tracks hate groups - as “a political party initially established by racist Southern California skinheads that aims to deport immigrants and return the United States to white rule.

“The group is now led by a coterie of prominent white nationalists, including corporate lawyer William D. Johnson, virulent antisemite Kevin MacDonald and white nationalist radio host James Edwards.”

Mark Potok, a senior fellow for the SPLC, called the organisation “arguably the most important white nationalist group in the country,” news site Mother Jones has reported.

In 2008, Mr Johnson attempted to run for the position Superior Court judge in California, only for his alter ego of James Pace to be unmasked by an anonymous agent working for the Simon Wiesenthal Centre.

During a Trump-promoting robocall which went out to Iowans ahead of the state caucus, Mr Johnson described himself to voters as “a farmer and a white nationalist.”