WASHINGTON — A day after he was convicted by a federal jury on bribery, money laundering, racketeering, fraud and other charges, Representative Chaka Fattah, Democrat of Pennsylvania, announced his resignation from Congress — but not until Oct. 3, just before his sentencing.

Mr. Fattah, who was found guilty of charges related to the misuse of campaign funds, faces a lengthy prison sentence, with some of the charges carrying potential sentences as high as to 20 years to life.

Mr. Fattah’s intention to remain in office despite his convictions drew swift outrage from the House speaker, Paul D. Ryan of Wisconsin, who called for Mr. Fattah’s immediate departure.

“Mr. Fattah has betrayed the trust of this institution and the people of Pennsylvania, and for that, he should resign immediately from the House of Representatives,” Mr. Ryan said in a statement. “We must hold members to the highest ethical standard, and I hope that Democratic leaders will join me in seeking his immediate resignation.”