The New Yorker said Monday that it had fired Ryan Lizza, the magazine’s Washington correspondent, after it said he had engaged in what it called “improper sexual conduct,” a charge that Mr. Lizza denied.

“The New Yorker recently learned that Ryan Lizza engaged in what we believe was improper sexual conduct,” a spokeswoman said in a statement. “We have reviewed the matter and, as a result, have severed ties with Lizza. Due to a request for privacy, we are not commenting further.”

Mr. Lizza rejected The New Yorker’s characterization of events, but both the magazine and Douglas H. Wigdor, a lawyer representing the woman accusing him of misconduct, said it was accurate.

In a statement, Mr. Lizza said the company’s decision to fire him “was made hastily and without a full investigation of the relevant facts” and “was a terrible mistake.”