Rudy Giuliani, one of Donald Trump’s primary lawyers during the former US president’s failed efforts to overturn the results of the 2020 election, is set to face professional ethics charges.

The move follows law licence suspensions in New York and the District of Columbia.

The US Office of Disciplinary Counsel, the disciplinary branch of the District of Columbia Bar, filed the charges against the former federal prosecutor and New York mayor alleging that he promoted unsubstantiated voter fraud claims in Pennsylvania.

The action was filed on June 6 and became public on Friday.

At issue are claims Mr Giuliani made in supporting a Trump campaign lawsuit seeking to overturn the election results in Pennsylvania.

That suit, which sought to invalidate as many as 1.5 million mail-in ballots, was dismissed by the courts.

The counsel’s office said Mr Giuliani’s conduct violated Pennsylvania Rules of Professional Conduct “in that he brought a proceeding and asserted issues therein without a non-frivolous basis in law and fact for doing so”, and “that he engaged in conduct prejudicial to the administration of justice”.

The counsel has asked the DC Court of Appeals Board on Professional Responsibility to take up the matter.

Mr Giuliani has 20 days to respond, according to the filing.

The step is the latest action against Mr Giuliani over his role in Mr Trump’s debunked claims that the 2020 presidential election was fraudulent.

Last June, an appeals court suspended Mr Giuliani from practicing law in New York because he made false statements while trying to get courts to overturn Mr Trump’s loss to Joe Biden.

An attorney disciplinary committee had asked the court to suspend his licence on the grounds that he had violated professional conduct rules as he promoted theories that the election was stolen through fraud.

The DC Bar temporarily suspended him last July, although the practical implication of that action is questionable, given that Mr Giuliani’s law licence in Washington has been inactive since 2002.

News of the counsel’s action follows the first public hearing by the US house committee investigating the Capitol riot on January 6 2021.

Mr Giuliani met the committee last month for several hours.