House Judiciary chairman Jerry Nadler says he has started formal impeachment proceedings against Donald Trump.

He added that his committee's investigation into the president could see articles of impeachment sent to the House floor by the end of the year.

Rep. Nadler even added that some impeachment articles had already been drawn up and told CNN that the committee is 'gathering evidence'.

The panel intends to see witnesses in September and October, including former White House counsel Don McGahn, a star witness of the Mueller Report who Democrats want to force to testify about his interactions with the president.

Nadler also praised House Speaker Nancy Pelosi and said his committee wouldn't have been able to file lawsuits to gather evidence against the President without her support and co-operation.

Pelosi previously shut down Nadler when he had proposed drafting articles of impeachment at the end of July.

House Judiciary chairman Jerry Nadler has revealed his committee is gathering evidence against Donald Trump as part of a formal impeachment investigation

Speaking to CNN host Erin Burnett, Nadler said: 'We are investigating facts, we are investigating evidence, we are going into court to get witnesses.'

He added that his committee had the power to recommend articles of impeachment and that they were gathering evidence with a view of doing just that.

In the interview, Burnett asked: 'In your mind, you're saying this is exactly the same as what we all call formal impeachment proceedings by another name?'

'This is formal impeachment proceedings. We are investigating all the evidence, we're gathering the evidence, and we will at the conclusion of this ― hopefully by the end of the year ― vote articles of impeachment to the House floor, or we won't. That's a decision that we'll have to make. But that's exactly the process we're in right now.'

The panel intends to see witnesses in September and October, including former White House counsel Don McGahn, a star witness of the Mueller Report who will be quizzed on his interactions with Donald Trump

Man who knows the secrets: Don McGahn was Trump's White House counsel but is now instructed not to give evidence to the House Judiciary Committee

Nadler's committee previously petitioned a federal judge to gain access to former special counsel Robert Mueller's grand jury testimony and is preparing to sue former White House Counsel Don McGahn for contempt of Congress after McGahn ignored the panel's subpoena at the White House' s request.

McGahn was a star witness in Mueller's report.

Nadler's panel is investigating whether Trump committed obstruction of justice in Mueller's investigation.

Mueller's report made no conclusion either way but, in his testimony before Congress, said his probe did not exonerate the president.

Attorney General William Barr did not pursue obstruction of justice charges.

Nadler outlined three items he's looking for before moving forward on impeachment: his committee must be able to prove the Trump committed impeachable offenses, those offenses much reach the threshold of serious impeachable offenses and they must have the support of the American people.

Democratic movers: Nancy Pelosi is confirming the go-ahead for a lawsuit against the White House to force Don McGahn to testify to Jerry Nadler's House Judiciary Committee

For Nadler's committee to move forward with impeachment proceedings, it would take 21 votes.

There are 25 Democrats on the committee and, currently, 16 support such an inquiry. Presumably, if it came to a vote, Nadler would support it, which would make 17.

It comes as recent court filings and public statements by top Democrats pointed to a dramatic escalation of a potential impeachment inquiry into the President.

House Speaker Nancy Pelosi says the House Judiciary Committee will file a complaint in federal court Wednesday aimed at forcing former White House counsel Donald McGahn to testify about his interactions with President Donald Trump.

The Democratic lawsuit is expected to challenge the White House rationale that McGahn and other witnesses have 'absolute immunity' from appearing and can defy subpoenas.