New York: The President's son has tweeted it, as has a prominent former White House adviser. Conservative websites such as Breitbart have published it. Republicans have uttered it during congressional hearings. You can find it on Google in a matter of seconds. Pretty much everyone in Washington's political class thinks they know it.

Yet no mainstream media outlet in the US has published the name of the alleged whistleblower who kickstarted the impeachment inquiry into Donald Trump. Even the hosts on Fox News have not unmasked the anonymous informant, although several presenters are clearly itching to do so.

US President Donald Trump says the whistleblower is partisan. Credit:Bloomberg

"I actually have multiple confirmations of who the whistleblower is," prime-time host Sean Hannity told his viewers this week. "But you know what? I’ll play the game for a little bit..."

Trump, not usually known for his social media restraint, has also held back from outing the CIA analyst who raised concerns about his phone call with Ukrainian President Volodymyr Zelensky.