US President Donald Trump has fanned the flames of a false conspiracy about Kamala Harris’ eligibility to be US Vice-President, fuelling an online misinformation campaign that parallels the one he used to power his rise into politics.

Asked about the matter at the White House, Mr Trump told reporters he had “heard” rumours that Ms Harris, a black woman and US-born citizen whose parents were immigrants, does not meet the requirements to serve in the White House.

The President said he considered the rumours about Ms Harris, who was tapped this week by Joe Biden to serve as his running mate on the Democratic ticket, to be “very serious”.

The conspiracy is demonstrably incorrect. Ms Harris, whose mother was born in India and father was born in Jamaica, was born in Oakland, California, and is eligible to be President and Vice-President under the constitutional requirements.

The 12th Amendment of the US Constitution states that “no person constitutionally ineligible to the office of President shall be eligible to that of vice president of the United States.”

Mr Trump built his political career on questioning a political opponent’s legitimacy. He was a high-profile force behind the “birther movement” – the lie that questioned whether Barack Obama, the nation’s first black president, was eligible to serve. Only after mounting pressure during his 2016 campaign did Mr Trump disavow the claims.

Mr Trump’s comments landed in a blizzard of other untrue, racist or sexist claims unleashed across social media and conservative websites after Mr Biden picked Ms Harris, the first black woman and the first Asian American woman on a major party ticket. The misinformation campaign is built on falsehoods that have circulated for months.

“I have no idea if that’s right,” said Mr Trump, who said he had read a column on the subject. “I would have assumed that the Democrats would have checked that out before she gets chosen to run for Vice-President.”

Mr Trump appeared to be referencing a Newsweek article by John Eastman, a conservative lawyer who argues the US Constitution does not grant citizenship to all people born in the US.

The column sought to raise questions about the citizenship of Ms Harris’ parents at the time of her birth, and argues that she may be “owed her allegiance to a foreign power or powers” if her parents were “temporary visitors” and not residents.

The question is not even considered complex, according to constitution lawyers. “Full stop, end of story, period, exclamation point,” said Jessica Levinson, a professor at Loyola Law School.

Not long after Mr Biden announced Ms Harris as his running mate, a crop of memes and conspiracy website posts began proliferating online, suggesting that the senator was an “anchor baby” because of her background.

A Republican National Committee spokesman said the party had no plans to challenge Ms Harris’s eligibility for the Democratic ticket.

-with agencies