US President Donald Trump’s lead lawyer for special counsel Robert Mueller’s investigation into Russian interference in the 2016 election has resigned.

Attorney John Dowd, 77, confirmed his departure in an email to news outlets on Friday morning (AEDT) saying: “I love the President and wish him well.”

The departure comes as the president has intensified his attacks on the Mr Mueller in recent weeks.

The Mueller probe should never have been started in that there was no collusion and there was no crime. It was based on fraudulent activities and a Fake Dossier paid for by Crooked Hillary and the DNC, and improperly used in FISA COURT for surveillance of my campaign. WITCH HUNT!

— Donald J. Trump (@realDonaldTrump) March 18, 2018

Mr Dowd said he made the decision voluntarily and denied reports that his departure was a response to Mr Trump ignoring his legal advice.

Other reports earlier stated Mr Trump had lost confidence in Mr Dowd’s ability to handle Mr Mueller.

“John Dowd is a friend and has been a valuable member of our legal team. We will continue our ongoing representation of the President and our cooperation with the Office of Special Counsel,” Jay Sekulow, another member of the President’s legal team, was quoted as saying by AP.

Mr Dowd has been Mr Trump’s lead lawyer since the middle of last year when he replaced then-lead lawyer Marc Kasowitz.

The departure follows Mr Trump’s addition of a new lawyer to his legal team who last week acused the FBI and the US Justice Department of trying to frame Mr Trump with false charges of collusion.

Over the weekend, Mr Dowd issued a statement calling for an end to the special counsel’s investigation, as Mr Mueller continued to close in on the President for questioning.

Mr Trump has told reporters he was eager to speak with Mr Mueller, but Mr Dowd was far more apprehensive, and the lawyers have not publicly committed to making the President available for questioning.

In a series of aggressive tweets towards Mr Mueller last week, the President said that the Russian probe should never have started, and that it was based on “fraudulent activities”.

Why does the Mueller team have 13 hardened Democrats, some big Crooked Hillary supporters, and Zero Republicans? Another Dem recently added…does anyone think this is fair? And yet, there is NO COLLUSION!

— Donald J. Trump (@realDonaldTrump) March 18, 2018

Mr Trump said that it was a “witch hunt” led by “13 hardened Democrats, some big Crooked Hillary supporters and zero Republicans”.

He once again insisted that there has been “no collusion”.

-with agencies