By David Thomas

July 21 (Reuters) - A group of Democratic U.S. lawmakers on Tuesday demanded law firm Skadden Arps provide additional details related to its deal with President Donald Trump to provide $100 million in free legal services, including information about its work advising chipmaker Intel INTC.O on its sale of a nearly 10% equity stake to the U.S. Commerce Department.

The lawmakers in a letter pressed Skadden executive partner Jeremy London for documents related to its Intel work, building on their prior demands for information from law firms that made deals with Trump last year.

Intel was sued earlier this year by a shareholder who alleged that the U.S. equity deal was unlawful and coerced by the White House. The shareholder lawsuit, which is pending in Delaware federal court, said Intel was "advised by legal counsel that itself was conflicted due to its pro bono promises to the president."

Senators Richard Blumenthal of Connecticut and Adam Schiff of California and Representative Jamie Raskin of Maryland said in Tuesday's letter that the "significant allegations of ethical impropriety in the Intel shareholder complaint" and Skadden's prior refusal to turn over documents "heighten our interest in understanding the details of your agreement with President Trump and any legal services Skadden has provided."

The lawmakers asked Skadden for any and all agreements with the White House and a list of all federal agencies the firm has worked for by August 4. They're also seeking a "detailed explanation of how Skadden’s advising of Intel in its transaction with the Trump Administration did not constitute a violation of the rules of professional conduct."

A Skadden spokesperson did not immediately respond to a request for comment. An Intel spokesperson declined to comment.

The White House in a statement called the Intel deal a bargain for taxpayers and criticized Democrats for not acknowledging "how President Trump has saved an iconic American company that’s critical for our domestic semiconductor manufacturing sector."

Skadden was one of nine major law firms that pledged to contribute a combined $940 million in pro bono work to causes supported by Trump, in order to head off a White House crackdown on firms that the president had accused of racial discrimination and acting against the country's interests.

Blumenthal, Schiff and Raskin previously in September asked Skadden for records relating to any work it has done for the U.S. government, following reports that Skadden and other firms were providing legal services to the Commerce Department.

Skadden in response did not say whether it had provided free or paid work to the government. It said in an October 7 letter that it chooses clients "in compliance with the highest ethical standards of the bar."

That letter "did not deny that Skadden has undertaken free legal work for a government agency," the Democratic lawmakers said Tuesday.

Under Intel's agreement with the Trump administration, the U.S. bought a 9.9% stake in Intel for $8.9 billion at a discounted share price.

Skadden represented Intel in a string of high-profile matters in recent years, including an $11 billion deal with Apollo Global Management APO.N related to Intel's manufacturing facility in Ireland.

Intel and the Commerce Department have each asked a federal judge to dismiss the shareholder complaint. Intel in a court filing said the lawsuit did not show Skadden's deal with Trump "manifested into a disabling conflict, or that Skadden in fact gave conflicted advice to Intel’s directors."

The full shareholder complaint was unsealed last month. Skadden is not a defendant in the case.