WASHINGTON — Representative Patrick Meehan, Republican of Pennsylvania, facing backlash after revelations that he settled a sexual harassment complaint brought by a former aide, will not seek re-election this year.

Mr. Meehan informed Speaker Paul D. Ryan of his decision in a letter sent on Thursday, according to Doug Andres, a spokesman for Mr. Ryan.

The decision is an abrupt reversal for Mr. Meehan, 62, who this week had insisted that he intended to run for re-election to a fifth term representing his suburban Philadelphia district, even as the House Ethics Committee investigated the sexual harassment allegations and his use of taxpayer money to settle them.

Mr. Meehan, a father of three, had faced increasing pressure to step down after The New York Times revealed on Saturday that a former aide decades his junior had filed a complaint against him last summer, and that Mr. Meehan had used his congressional office fund to pay her thousands of dollars to settle it. She had accused him of making unwanted romantic overtures to her after he learned that she had developed a serious relationship with a man closer to her age. After the aide rebuffed Mr. Meehan, he became hostile, her complaint said.