Facebook said that it had seen “signals” that the story might be false and reduced the story’s prominence in users’ news feeds until it could be examined by independent fact-checkers while Twitter claimed that the story might be based on “hacked materials” and warning users that the link could be “unsafe” before letting them click through.
The emails were reportedly found on a laptop computer abandoned at a repair shop in Delaware last year.
According to the New York Post the repair shop owner discovered them and contacted the FBI, who took the computer in December.
The shop owner also reportedly made a copy of the hard drive, which found its way to Mr Giuliani, according to the New York Post.
Last year, Mr Trump was impeached over allegations he sought to pressure Volodymyr Zelenskiy, the Ukrainian president, to launch an investigation into the Bidens and Burisma. The president was later acquitted after a Senate trial.
Mr Biden has always maintained he never discussed his son’s business dealings with Burisma while he was handling Ukraine policy for the Obama administration.
Mr Bates, the Biden campaign spokesman, said: “Investigations by the press, during impeachment, and even by two Republican-led Senate committees… have all reached the same conclusion: that Joe Biden carried out official US policy toward Ukraine and engaged in no wrongdoing.
“The New York Post never asked the Biden campaign about the critical elements of this story.”