Updated at 7 p.m.

A senior lawyer in the U.S. House of Representatives general counsel's office is leaving the legislative chamber's legal team as the Democratic majority ramps up investigations into President Donald Trump and his administration, setting the stage for court battles over document demands.

The lawyer, Kimberly Hamm, notified judges in pending cases that she is stepping down from her role as associate general counsel. A former litigation counsel at the law firm Simpson Thacher & Bartlett, Hamm joined the House general counsel's office in October 2014 and was promoted last year, under the leadership of then-general counsel Thomas Hungar, to the third-ranking role in the office.

Hamm's departure comes just months after the Democrats returned to power in the House and Douglas Letter, a former top Justice Department appellate lawyer, was named by Speaker Nancy Pelosi, D-California, as the new general counsel. Hungar returned to his former firm, Gibson, Dunn & Crutcher, as a partner in January.

Last month, Letter hired Megan Barbero, a senior appellate lawyer at the Justice Department, as an associate general counsel. As of Tuesday, Barbero and Hamm were both identified as associate general counsels on the House general counsel office's website.

Hamm did not return messages seeking comment. Letter referred questions to Pelosi's office, which did not immediately respond to a request for comment.

A person familiar with Hamm's plans said she is joining the U.S. Securities and Exchange Commission as an adviser to Chairman Jay Clayton.

Hamm has made appearances in court cases in which the House has asserted its voice as an institution. Those cases have involved public-records disputes, subpoena fights and health care matters.

On Tuesday, Hamm alerted U.S. District Judge Emmet Sullivan of the District of Columbia of her departure in a case involving a government watchdog group's request for communications between the White House, Department of Health and Human Services and Congress related to the Republicans' ultimately failed effort to repeal the Affordable Care Act.

The House general counsel's office, then led by Hungar, intervened on behalf of the House Ways and Means Committee in September 2017, arguing against the disclosure of congressional records he claimed were confidential.

Hamm's notice, a common filing for government lawyers who leave public service, said a colleague, Kristin Shapiro, an assistant general counsel in the office, would continue representing the House committee in the litigation.

Shapiro joined the general counsel's office in 2016 from Williams & Connolly, where she had been an associate. The office has one other assistant general counsel, Brooks Hanner, who joined the office from Hogan Lovells in July. He had been a senior associate there.

Hamm had previously helped defend the House against former FBI Director James Comey's bid to block a subpoena. Comey, represented by Dechert partners David Kelley and Vincent Cohen, eventually dropped his challenge after reaching what he called an “acceptable accommodation” to testify voluntarily.

Hamm leaves the House general counsel's office as Democrats appear increasingly poised to pursue documents from the Trump administration.

On Monday, the leaders of six House committees sent a letter to Attorney General William Barr demanding the full release of Special Counsel Robert Mueller III's report on the investigation into Trump and Russia's interference in the 2016 election. The House Judiciary Committee on Wednesday plans to begin authorizing subpoenas demanding the report, along with underlying evidence and materials.

“While we hope to avoid resorting to compulsory process, if the department is unwilling to produce the report to Congress in unredacted form, then we will have little choice but to take such action,” the committee leaders said.