WASHINGTON (Reuters) - A senior Democratic lawmaker has suggested fines of $25,000 a day for contempt on U.S. officials who stonewall congressional investigations of President Donald Trump and his administration.

Expanding on an idea floated days ago by Democrats as a way of putting some teeth into various inquiries of Trump, his turbulent presidency, his family and his business interests, Representative Adam Schiff spoke in two interviews about reviving the “inherent contempt” power of Congress.

“We would levy fines on those who are not cooperating,” Schiff, the chairman of the U.S. House of Representatives Intelligence Committee told Axios in an interview published on Friday.

“You could fine someone $25,000 a day until they comply. You can do that. We’re looking through the history and studying the law to make sure we’re on solid ground,” Schiff said.

Democrats who control the House have confronted the Republican president and his administration for refusing to cooperate with at least six separate investigations. Republicans have accused Democrats of grandstanding for progressive voters, but even the Republican-controlled Senate Intelligence Committee has subpoenaed the president’s son, Donald Trump Jr.

Congress can subpoena testimony and documents, then enforce these formal requests by holding recalcitrant subpoena targets in contempt of Congress. At that point, legal options are less clear cut.

Congress can ask federal prosecutors to take the matter to court, but legal experts have questioned the effectiveness of this option since prosecutors work for the Justice Department whose top official is appointed by Trump.

Congress can go to court itself and ask a judge to step in, but this can be time consuming. Finally, opening an impeachment proceeding adds force to congressional inquiries, but Democratic leaders have been reluctant to take this rare step.

Democrats instead are exploring inherent contempt, a dormant, extrajudicial power to arrest, detain and fine that Congress has not used since the 1930s.

Schiff talked about reviving inherent contempt and imposing fines on The Rachel Maddow Show on MSNBC on Thursday. He said such a step by Congress “may be even quicker than the impeachment proceeding or the court proceeding.”

U.S. Attorney General William Barr, a Trump appointee, has been cited for contempt by the House Judiciary Committee for refusing to hand over an unredacted copy of the Mueller report on Russian election interference and any ties to the 2016 Trump campaign. The administration invoked executive privilege to keep the full Congress from seeing the report.

House Judiciary Committee Chairman Jerrold Nadler raised inherent contempt as a possibility last week.

Under inherent contempt, the House sergeant-at-arms can arrest and detain people. Democratic leaders have said they have no plans to revive that power.

“It used to be we imprisoned people,” Schiff said on MSNBC. “But we could also fine them $25,000 a day until they comply, or some other number.”

Exactly how that would work is uncertain. Some legal experts have said fines could be imposed, but that it might require passage of enabling legislation by Congress.

Trump has openly vowed to fight congressional subpoenas and directed top officials not to comply. On Friday, Nadler said his panel had again issued a subpoena to former White House counsel Don McGahn and that lawmakers expect him to appear May 21 or face being cited for contempt, according to Fox News.