US President Donald Trump has called for the whistleblower who triggered the impeachment inquiry to be unmasked, ignoring a cease-and-desist warning.

On Thursday a lawyer for a whistleblower told the White House that Mr Trump’s rhetoric was placing his client and family in physical danger.

Undeterred by the letter, Mr Trump renewed his attacks on the whistleblower and lawyer on Friday.

The individual’s identity has so far been fiercely guarded by Democrats.

In August the whistleblower filed a report that eventually triggered impeachment proceeding against Mr Trump.

The report expressed concern over a phone call a month earlier in which Mr Trump asked his Ukrainian counterpart Volodymyr Zelensky to investigate Joe Biden, a Democratic front-runner for the 2020 US presidential election.

In Thursday’s letter, sent to White House counsel Pat Cipollone, the whistleblower’s lawyer Andrew Bakaj cites many examples of the president’s “fixation” on the identity of his client in his comments to the media, at rallies and on Twitter.

“Such statements seek to intimidate my client – and they have,” Mr Bakaj writes.

He continued: “Should any harm befall any suspected named whistleblower or their family, the blame will rest squarely with your client.”