Trump impeachment: More stonewalling likely as White House says Senate can’t subpoena senior advisers

Even in the event that the Senate decides to hear from the witnesses requested by Democrats the White House intends to continue blocking them from testifying.

Senate majority leader Mitch McConnell has already rejected Democrats' call to hear from several witnesses at Donald Trump's upcoming impeachment trial, but it may not matter if Democrats can find enough Republican votes to allow witness testimony.

Even in the event that the Senate decides to hear from the witnesses requested by Democrats - including White House acting chief of staff Mick Mulvaney, office of management and budget official Michael Duffey, Mulvaney aide Robert Blair, and former national security advisor John Bolton - the White House intends to continue blocking them from testifying.

Since House Democrats announced their impeachment inquiry in October, the White House's position has been that Mr Trump and his aides are not required to comply with congressional subpoenas because White House counsel Pat Cipollone found the inquiry to be "constitutionally invalid and a violation of due process".

"In order to fulfil his duties to the American people, the constitution, the executive branch, and all future occupants of the office of the presidency, President Trump and his administration cannot participate in your partisan and unconstitutional inquiry under these circumstances."

But despite the White House's prior claims that administration officials did not need to participate in the House's "illegitimate" inquiry, a senior White House official told The Independent that the president would refuse to produce witnesses for his own impeachment trial, even if the Senate agreed to issue subpoenas for testimony.

"The subpoena issues remain the same. Whether they come from the House or Senate is neither here nor there, these are senior advisors to the president who enjoy immunity," said the official, who was not authorised to discuss the president's legal strategy on the record.

When asked why the White House would not honour a subpoena from the Republican-controlled Senate after months of complaints that the process followed in House Democrats' inquiry was unfair, the official blamed Democrats once again.

"It's not the president's fault that Democrats put together such a slapdash accusation and failed to secure the testimony of these witnesses during the impeachment inquiry in the House because they were working on an artificial and political timetable and didn't want to wait until the issue worked its way through [the courts]," the official said.

The official added that the refusal to allow witnesses to testify in a Senate impeachment trial is simply the Trump administration following a practice - supposedly dating back to the Clinton administration - of claiming immunity from testimony for top White House advisers.

But the official also claimed that the White House's previous process arguments have nothing to do with why presidential advisers would not have to testify in a Senate trial, calling it a "separation of powers issue".

"There's no legal difference between a House subpoena for an inquiry and a Senate subpoena for a trial," the official said. "The basis for withholding members of the president's senior staff for the inquiry did not rise and fall on the inherent unfairness of the House process. They are immune from compelled testimony and that is the legal basis upon which they did not appear."