Trump administration staff who are protecting the president by refusing to comply with congressional subpoenas could abandon him under threat of huge fines, senior Democrats have suggested.

Adam Schiff, Democratic chair of the House intelligence committee, has proposed holding those who do not comply with Congress with inherent contempt, a rarely used procedure which can result in fines up to $25,000 (£19,330) daily or even imprisonment.

The proposal comes amid an unprecedented effort by the White House to resist efforts by House Democrats to get access to Donald Trump’s tax returns, the unredacted Mueller report, and documents from former White House lawyer Don McGahn.

"I don't know how many are going to want to take that risk for Donald Trump. But we're going to have to use that device if necessary," Mr Schiff told ABC News.

"We’re going to have to use the power of the purse if necessary. We're going to have to enforce our ability to do oversight.”

Democratic congressman Ro Khanna, asked about Mr Schiff’s comments, told NBC News on Monday that he believed “fines would be appropriate”.

Noting the threat of contempt ultimately pressured the Nixon administration into complying with Congress during the Watergate scandal, Mr Khanna said: “I do think it could be a game changer. Not everyone is going to want to incur a fine to protect this president, not everyone is going to want to be held in contempt of congress to protect this president.”

Mr Khanna, who is co-chair of Bernie Sanders’ 2020 presidential campaign, added he hoped the issue could be resolved in the courts, amid what he described as a “constitutional stalemate".

House Democrats last week escalated their feud with the White House by moving towards holding attorney general William Barr in contempt over his refusal to give up the unredacted Mueller report, which details Russia's attempts to help Mr Trump win the 2020 election, as well as the president's attempts to impede the subsequent investigation.

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Finding Mr Barr in contempt would make him only the second sitting attorney general to be hit with the charge.

The White House has been contacted for comment.