Rudy Giuliani has said he will not co-operate with an impeachment inquiry against Donald Trump and insisted he did not need a lawyer following the arrest of two business associates accused of campaign finance violations.

The president’s personal attorney posted a letter on Twitter to the House permanent select committee on intelligence in which his lawyer wrote: “Please accept this response as formal notice that Mr Giuliani will not participate because this appears to be an unconstitutional, baseless and illegitimate ‘impeachment inquiry.’”

The attorney to Mr Giuliani — who was subpoenaed by Congress over documents related to the impeachment inquiry — said the subpoena was “overbroad, unduly burdensome, and seeks documents beyond the scope of legitimate inquiry” in the letter dated 15 October.

In his tweet posted on Tuesday afternoon, Mr Giuliani also announced his own lawyer, Jon Sale, would no longer represent him.

Mr Giuliani described Mr Sale — who he reportedly hired just 14 days ago — as a “lifelong friend” who represented him “for the sole purpose of analysing the request and responding.”

“At this time, I do not need a lawyer,” he added.

Mr Giuliani’s letter comes on the day of the deadline for him to comply with the congressional subpoena sent by three House committees spearheading the impeachment inquiry into Mr Trump.

Democrats on Capitol Hill say Mr Giuliani was seeking foreign dirt on Mr Trump’s 2020 political rival Joe Biden in Ukraine. The president had a 25 July phone call with Ukrainian President Volodymyr Zelensky in which he asked for a “favour” and then urged Mr Zelensky to launch an investigation into Mr Biden and his son, Hunter, who worked for a Ukrainian energy firm.

There has so far been no evidence of illegal wrongdoing by either of the Bidens. Mr Giuliani, meanwhile, is under increasing scrutiny among federal prosecutors over accusations of illegal lobbying in another country without registering as a foreign agent.

Experts previously told The Independent in July that Mr Giuliani must register as a foreign agent for his overseas work. Mr Giuliani has denied the allegations.

It remains unclear what could happen next, though Mr Giuliani will almost certainly require legal representation if the House committees seek to enforce their subpoena against him.

Support free-thinking journalism and attend Independent events