Related video: Ro Khanna suggests Donald Trump administration officials could be fined for ignoring subpoenas

The president has tweeted angrily about the hearing taking place behind closed doors on Capitol Hill, writing: “Why aren’t the Dems looking at the 33,000 Emails that Hillary and her lawyer deleted and acid washed AFTER GETTING A SUBPOENA FROM CONGRESS? That is real Obstruction that the Dems want no part of because their hearings are RIGGED and a disgrace to our Country!”

Last night, Mr Trump kicked off his 2020 re-election campaign in Orlando, Florida, tearing into his enemies in Washington and pledging to combat “criminal aliens” in a wild address at the 20,000-capacity Amway Center packed with his most ardent supporters.

Less than an hour into Ms Hicks’ interview on Wednesday, frustrated Democrats taking breaks from the meeting said she and her lawyer were following White House orders to stay quiet about her time working for Mr Trump.

She was answering some questions about her time on the campaign, however, the lawmakers said.

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“She’s objecting to stuff that’s already in the public record,” said California Democrat Karen Bass. “It’s pretty ridiculous.”

Pramila Jayapal, a Washington Democrat, called her answers “a farce.” Ted Lieu, a California Democrat, tweeted about the interview and wrote that Ms Hicks refused to answer even innocuous questions such as whether she had previously testified before Congress.

House Judiciary Committee Chairman Jerrold Nadler declined to comment on the substance of the interview so far, saying “all I’ll say is Ms Hicks is answering questions put to her and the interview continues.”

Republicans had a different perspective, saying she was cooperative and that the interview was a waste of time. The top Republican on the panel, Doug Collins, said they were “simply talking about things that are already out there in public or getting the same answers over and over.”

It was so far unclear whether Democrats would take Ms Hicks or the administration to court to challenge the claim of immunity. In a letter Tuesday to Mr Nadler, White House counsel Pat Cipollone wrote that Mr Trump had directed Ms Hicks not to answer questions “relating to the time of her service as a senior adviser to the president.”