A fourth US lawmaker has been forced out of Congress amid allegations of sexual misconduct.

Representative Blake Farenthold, a Republican from Texas, will not seek re-election in 2018, the House speaker, Paul Ryan, announced on Thursday.

Speaking at a press conference on Capitol Hill, Ryan told reporters Farenthold was “making the right decision to retire”.

Farenthold’s office has yet to issue a statement.

The decision came one day after a former staffer alleged “verbally abusive and sexually demeaning” behavior in an interview with CNN.

Michael Rekola, who served as Farenthold’s communications director in 2015, accused Farenthold of making sexually graphic jokes and regularly referring to his aides as “fucktards”.

Rekola also said Farenthold would angrily berate his aides and that the congressman’s bullying led him to seek psychological counseling and medical treatment.

“There are news stories that are very disconcerting,” Ryan said. “Unacceptable behavior has been alleged in those stories, and I think he’s made the right decision that he’s going to be leaving Congress.”

Farenthold was already under investigation by the House ethics committee after it was revealed earlier this month that he used taxpayers’ money in 2014 to settle a sexual harassment claim brought by his former spokeswoman.

Lauren Greene, then Farenthold’s communications director, had filed a lawsuit against Farenthold in the US district court in the District of Columbia over allegations of sexual harassment and gender discrimination.

Greene alleged she was fired after complaining about Farenthold’s behavior. She dropped the case after reaching a private settlement with the congressman.

Ryan would not say if he believed Farenthold should immediately resign.

According to a source familiar with the discussion, Ryan spoke with Farenthold on Wednesday and urged him not to run for another term.

Farenthold is the latest member of Congress whose political career has been cut short amid a watershed dialogue regarding sexual misconduct.

Last week, the Arizona representative Trent Franks resigned after it was alleged he discussed surrogacy issues with female staffers. Franks, a Republican, reportedly offered an aide $5m to bear his child.

Two Democrats, the Minnesota senator Al Franken and the Michigan representative John Conyers, also resigned this month following sexual harassment allegations.

Several women accused Franken of grabbing their rear ends while posing for photographs, while two other women said he tried to forcibly kiss them. Franken denied the claims but resigned after a growing number of Democrats called on him to step down.

Conyers also resigned at the urging of his Democratic colleagues after it was revealed he reached a $27,000 settlement with a female staffer who said she was fired because she resisted the congressman’s sexual advances.

This week, a group of Democratic lawmakers called for a congressional investigation into sexual assault allegations against Donald Trump. The president was accused of sexual misconduct by as many as 17 women prior to his election last November.

Republican leaders have said they do not plan to launch in inquiry into Trump, who has denied the allegations. Trump, however, boasted of groping and kissing women without their consent in a 2005 Access Hollywood tape leaked less than two months before the presidential election.