A Democratic lawmaker resigned Tuesday, becoming the third member of the US House of Representatives to step down in just over a week as a wave of ethics scandals engulfs Congress.

Sheila Cherfilus-McCormick of Florida announced her immediate resignation ahead of a scheduled disciplinary hearing by the House Ethics Committee, which had been weighing potential sanctions over a string of campaign finance violations.

Her departure follows the resignations of Democrat Eric Swalwell and Republican Tony Gonzales, who stepped down amid separate sexual misconduct allegations, fueling a rare bipartisan reckoning over lawmakers' treatment of staff in Congress.

Cherfilus-McCormick had been accused of diverting millions of dollars in federal disaster funds for political purposes and is facing a federal criminal case. She denies wrongdoing and has pleaded not guilty.

In a statement, she denounced the process as unfair, saying the Ethics Committee "refused my new attorney's reasonable request for time to prepare my defense" and describing the proceedings as "a witch hunt."

"I simply cannot stand by and allow my due process rights to be trampled on, and my good name to be tarnished," she said, adding that she would focus on fighting for her community outside Congress.

The Ethics Committee had found Cherfilus-McCormick responsible for 25 violations, citing the scale and persistence of the alleged conduct.

The spate of cases has shaken a narrowly divided House, where pressure has mounted on leaders of both parties to enforce ethical standards even as political calculations complicate disciplinary action.

Democratic Virginia Congressman Suhas Subramanyam, a member of the Ethics Committee, said the wave of scandal and trio of resignations was "not a good message" to send to the American people. 

"I think, in the end, Congress is losing the trust in the American people every time something like this happens." he told reporters. 

The latest resignation shifts attention to Republican Cory Mills, who remains under investigation over allegations including sexual misconduct, campaign finance violations and misuse of his office, all of which he denies.