A former United States representative from Texas and one of his aides were indicted on Tuesday on charges that they stole hundreds of thousands of dollars meant for charity, some of which was used to illegally finance his campaigns.

The former representative, Steve Stockman, 60, and the former director of special projects in his congressional office, Jason Posey, 46, were charged in a 28-count indictment related to the alleged yearslong fraud scheme. The charges included mail and wire fraud, conspiracy, making false statements to the Federal Election Commission and money laundering, the Justice Department said in a statement.

Mr. Stockman, a Republican, solicited $1.25 million in charitable donations from May 2010 to October 2014 that was later used for other purposes, the Justice Department said.

Dane Ball, who represents Mr. Stockman along with his colleagues at the law firm Smyser Kaplan & Veselka, said the former congressman plans to plead not guilty.