Following years of investigation, the Department of Justice has informed lawyers for at least one witness that it will not bring charges against Representative Matt Gaetz over his potential role in sex-trafficking.

The Justice Department, which does not normally comment when it fails to take action, has not commented on the case, but officials with Mr. Gaetz’s office said the Republican of Florida will not face charges. CNN first reported the developments on Wednesday.

“We have just spoken with the D.O.J. and have been informed that they have concluded their investigation into Congressman Gaetz and allegations related to sex trafficking and obstruction of justice and they have determined not to bring any charges against him,” Mr. Gaetz’s lawyers, Isabelle Kirshner and Marc Mukasey, said in a statement.

For Mr. Gaetz, the development marks the end of an investigation that began in the final months of President Trump’s administration when an associate of his, a former tax collector, Joel Greenberg, pleaded guilty to an array of charges, including sex trafficking of a minor. Greenberg was sentenced to 11 years in prison two months ago.

The Department of Justice was investigating whether the 40-year-old Mr. Gaetz had a sexual relationship with a 17-year-old girl and paid for her to travel with him or paid her to have sex with him.

Federal investigators had reportedly identified a 2018 trip Mr. Gaetz made to the Bahamas, allegedly alongside a 17-year-old who was introduced by Greenberg, as a key event in their investigation.

Greenberg’s 2021 guilty plea was seen as an ominous sign for Mr. Gaetz. In 2022, an ex-girlfriend of Mr. Gaetz’s had also agreed to testify in front of a grand jury in exchange for immunity.

The news that Mr. Gaetz would not be facing charges comes as he wields more leverage in the House of Representative than ever before.

Mr. Gaetz was a key holdout in the election of the speaker of the House in January and a leader of a group that negotiated to extract concessions from Speaker McCarthy ranging from spending cuts to rules changes.

Among these concessions — not all of which were made public — was the restoration of a one-member motion to vacate, meaning that any single member of the House can call a vote of no confidence in the speaker at any time.

The concessions have led to a historically weak speakership for Mr. McCarthy, who will have to find a way to please every single member of his raucous Republican conference in a number of key battles this year, most notably in dealing with the debt ceiling.