The Democratic chairman of the House judiciary committee has issued a subpoena ordering that the former White House counsel Don McGahn testify before Congress. The move came as the House speaker, Nancy Pelosi, vowed to hold Donald Trump to account following the release of Robert Mueller’s report on Russian influence on the 2016 US election.

Giuliani rails against Mueller report as Democrats mull Trump impeachment Read more

The subpoena, issued on Monday, escalates the congressional investigations into Trump, his finances and accusations that he sought to obstruct justice, as Democrats debate how to proceed with the evidence contained in the special counsel’s 448-page report. McGahn cooperated extensively in the special counsel’s investigation and emerged as a key witness in several incidents at the heart of whether Trump obstructed justice.

“The special counsel’s report, even in redacted form, outlines substantial evidence that President Trump engaged in obstruction and other abuses,” said Jerry Nadler, the chairman of the House judiciary committee, which has the power to launch impeachment proceedings.

“It now falls to Congress to determine for itself the full scope of the misconduct and to decide what steps to take in the exercise of our duties of oversight, legislation and constitutional accountability.”

Sign up for the US morning briefing

In a statement, Nadler said the committee asked for McGahn to turn over documents and records related to the federal investigations into Trump by 7 May and to testify before his committee by 21 May.

Meanwhile, at a prime-time town hall meeting of five Democratic presidential contenders on Monday in New Hampshire, the California senator Kamala Harris said Congress should “take the steps towards impeachment” but believed such an effort would probably fail.

Only one candidate at the event, Massachusetts senator Elizabeth Warren, issued a full-throated call for Congress to try to remove Trump from office. “If any other human being in this country had done what’s documented in the Mueller report, they would be arrested and put in jail,” Warren said

Nadler had issued the subpoena for McGahn as Democrats came together for the first time since the report was released on a conference call to discuss how the House would proceed.

Nancy Pelosi cautioned Democrats against hastily moving toward impeachment, making clear that their immediate focus would be on investigating the president and that those inquiries would guide their actions.

“This isn’t about Democrats or Republicans,” Pelosi told her colleagues, according to multiple officials on the call. “It’s about saving our democracy.”

Ahead of the call, Pelosi acknowledged the divide within her caucus over whether to pursue impeachment – a step supported by many on the party’s left flank, including 2020 contenders Elizabeth Warren and Julián Castro.

“While our views range from proceeding to investigate the findings or proceeding directly to impeachment, we all firmly agree that we should proceed down a path of finding the truth,” Pelosi said in a letter to her colleagues. “It is also important to know that the facts regarding holding the president accountable can be gained outside of impeachment hearings,” she wrote.

She vowed that Democrats would “scrupulously assert Congress’s constitutional duty to honor our oath of office to support and defend the constitution and our democracy” by escalating its investigation into the president.

She added: “Whether currently indictable or not, it is clear that the president has, at a minimum, engaged in highly unethical and unscrupulous behavior which does not bring honor to the office he holds.”

In her letter, Pelosi also admonished congressional Republicans – who, with a few notable exceptions, have largely fallen in line and supported Trump’s assessment that the report clears him of wrongdoing – for what she called an “unlimited appetite for such low standards” set by the president.

“The GOP should be ashamed of what the Mueller report has revealed, instead of giving the president their blessings,” she wrote.

This is the second subpoena issued by Nadler since the release of the report: on Friday he demanded that the justice department turn over an unredacted version of the report as well as the underlying evidence by 1 May, when the attorney general, William Barr, is due to testify before Congress. Nadler, a New York Democrat, has also invited Mueller to testify before his committee next month.

The Republican congressman Doug Collins, the ranking member of the House judiciary committee, called the subpoenas “premature” and criticized Democrats for seeking delicate information that the justice department believes should remain confidential.

“Instead of looking at material that Attorney General Barr has already made available, Democrats prefer to demand more documents they know are subject to constitutional and common-law privileges and can’t be produced,” he said.

Barr offered to brief a select, bipartisan group of lawmakers on a version of the report that was less redacted than the copy made public. Democrats refused the offer arguing that Congress is entitled to the full, unredacted report.

Trump has maintained that the report represents a “total exoneration” and has insisted repeatedly that there are no grounds for impeachment. After the subpoena was issued, he tweeted: “PRESIDENTIAL HARASSMENT”.

Trump and impeachment: where Democrats stand after Mueller Read more

This weekend, senior Democrats blanketed TV talkshows and refused to rule out impeachment. However, they remained firm that there was more to investigate before making a final determination.

“I do think, if proven – which hasn’t been proven yet – if proven, some of this would be impeachable, yes,” Nadler said NBC’s Meet the Press on Sunday. “Obstruction of justice, if proven, would be impeachable.”

Democrats believe Mueller’s report offered them a “roadmap” to further investigate Trump for obstruction of justice. They point to a passage from the report, in which Mueller writes: “Congress has authority to prohibit a president’s corrupt use of his authority in order to protect the integrity of the administration of justice.”