(Reuters) -A prominent Washington lawyer who launched a new firm this year to represent officials targeted by President Donald Trump is quickly gaining new clients, including Federal Reserve Governor Lisa Cook and U.S. Centers for Disease Control and Prevention Director Susan Monarez.

Abbe Lowell, whose clientele includes Hunter Biden and New York Attorney General Letitia James, filed a lawsuit on Thursday on Cook's behalf, alleging Trump's effort to fire her over mortgage fraud allegations is unlawful.

Monarez this week also turned to Lowell, along with fellow longtime Washington lawyer Mark Zaid, after the White House said on Wednesday she was being fired. Lowell and Zaid in a statement accused Health and Human Services Secretary Robert F. Kennedy Jr. of targeting Monarez for refusing to support "unscientific directives" and dismiss health experts.

Zaid, known for his legal work on national security matters and for whistleblowers, is also a plaintiff in a lawsuit Lowell filed on his behalf in May after the Trump administration stripped Zaid of his U.S. security clearance.

Cook was appointed by Democratic former President Joe Biden in 2022 and is the first African-American woman to serve on the U.S. central bank's governing body.

Trump in a letter announcing his move to fire Cook on Monday said he had "sufficient cause to remove you from your position" because in 2021 she had indicated on documents for separate mortgage loans on properties in Michigan and Georgia that both were a primary residence where she intended to live. 

Cook has denied wrongdoing and has not been charged.

In Cook's lawsuit, Lowell and attorney Norm Eisen, who served as co-counsel for the U.S. House of Representatives Judiciary Committee in the first impeachment of Trump in 2020, called the Republican president's bid to remove Cook from the politically independent Fed "unprecedented and illegal."

Monarez has so far not filed a lawsuit over her attempted ouster from the CDC.

NEW FIRM

Lowell was a partner at major U.S. law firms before announcing in May that he was opening his own firm to represent government officials under fire by the Trump administration. 

He represented Biden's son Hunter against criminal gun and tax charges before he was pardoned in December. He has also represented former Democratic U.S. Senator Bob Menendez, failed Democratic U.S. presidential candidate John Edwards, Trump's daughter Ivanka Trump, and Trump's son-in-law Jared Kushner.

New York's attorney general James hired Lowell after the Trump administration referred her to the Justice Department for allegedly falsifying real estate records. James has denied the allegations.

Lowell is also a lead attorney in a lawsuit filed in July accusing the Justice Department of illegally firing three former government employees, including a lawyer who prosecuted people involved in the January 6, 2021, attack on the U.S. Capitol.

His new firm employs two former lawyers at Skadden Arps who quit over its response to Trump's executive orders targeting the legal profession. Skadden is one of nine law firms that cut deals with the administration to avoid Trump's crackdown on firms he accused of "weaponizing" the legal system, while four other firms successfully sued.