Sumner Redstone, the media mogul, on Tuesday sued two ex-girlfriends over civil claims including elder abuse, saying he was forced to borrow $100 million from the private company that holds his voting shares of CBS Corporation and Viacom to cover tax obligations on gifts he gave to the women.

The lawsuit, filed in Los Angeles Superior Court, seeks about $150 million that Mr. Redstone’s lawyers say he gave to his former girlfriends Manuela Herzer and Sydney Holland. Mr. Redstone’s lawsuit is the newest front in a nearly yearlong litigation war between Mr. Redstone, the 93-year-old former Viacom chairman, and Ms. Herzer.

Ron Richards, a lawyer for Ms. Herzer, said the lawsuit had no merit. “All of the gifts Mr. Redstone made to my client and to Sydney Holland were made with his full knowledge and blessing,” he said.

In a statement, Ms. Holland called the lawsuit “fictional revisionist history.” She said that Mr. Redstone’s lawyers and doctors “vetted and approved all payments” she received.