In the memo first reported by NBC News, Biden’s campaign accuses President Donald Trump of "spreading a malicious and conclusively debunked conspiracy theory" that the former VP engaged in wrongdoing when he pressured Ukraine to fire former Prosecutor General Viktor Shokin.

Biden has previously bragged about his role in having Shokin fired, even admitting on camera that he presented an ultimatum to Ukrainian authorities, threatening to withhold a billion-dollar loan guarantee unless the prosecutor was given the boot. It emerged later that Biden’s own son Hunter sat on the board of the Burisma energy company which Shokin had been investigating for corruption.

The memo, described as “unusual” by NBC News, demands that "any media organization referencing, reporting on, or repeating” claims that Biden engaged in wrongdoing "must state clearly and unambiguously that they have been discredited and debunked by authoritative sources."

The memo instructs journalists that it is “not sufficient” to say allegations against the Democratic candidate are “unsubstantiated.” They must tell readers there is a mountain of evidence which debunks them, it says. Any journalists or media organizations failing to adhere to Biden’s standards in their reporting on his and his families’ activities in Ukraine are accused of “malpractice.”

The memo comes as Republicans call for Hunter Biden to testify during Donald Trump's impending Senate impeachment trial. Trump was impeached last month by the US House Representatives for “abuse of power” and “obstruction of Congress” relating to the alleged claim that he withheld aid from Ukraine in an effort to force an investigation into Biden’s involvement with Burisma and his role in Shokin’s firing.