The bitter feud between Howard Stern and his former bosses headed to the courts yesterday after CBS Radio filed suit against the radio “shock jock,” claiming Mr. Stern’s on-air antics breached his contract and cost the network hundreds of millions of dollars.

The network’s announcement of a lawsuit came hours after Mr. Stern tried to pre-empt CBS’s claims by holding a hastily scheduled news conference to accuse network officials of “bullying” and “threatening” him.

In a much-hyped move, Mr. Stern took his popular radio talk show to subscription-based Sirius Satellite Radio in January after the expiration of his contract at CBS Radio, formerly known as Infinity Broadcasting Corporation.

In a lawsuit filed in New York State Supreme Court, CBS claims that Mr. Stern, in “flagrant disregard” of his contract, made a secret agreement with Sirius to promote the network while he was still working for CBS. The suit further alleges that Mr. Stern gave Sirius “millions of dollars in free advertising” by using his CBS show to promote satellite radio. It says that Sirius rewarded him for the resulting boost in subscriptions with a payout in January of $220 million in stock.

Mr. Stern said he was offended by the network’s accusations, which he called a “personal vendetta” on the part of CBS chief Leslie Moonves. The lawsuit, Mr. Stern said, is an attempt to distract attention from the ratings drop-off the radio network has suffered since he left.

Mr. Stern called the charges unfounded and rejected the notion that his deal with Sirius was a secret, citing heavy news coverage of the agreement. “How can there be a secret if everybody, including his radio stations, are broadcasting the deal? Where’s the secret, Les?” Mr. Stern said, speaking to reporters at the Times Square offices of his attorney, L. Peter Parcher.

Mr. Parcher is a partner at Manatt, Phelps & Phillips, the same firm where a GOP gubernatorial hopeful, John Faso, is a partner. Mr. Faso declined to comment on the Stern case.

Referring to the charge that he used CBS airtime to promote Sirius, Mr. Stern said the head of CBS Radio, Joel Hollander, had consented to how Mr. Stern would discuss satellite radio on his show, and even told Mr. Stern he thought Mr. Stern’s veiled references to Sirius were funny. CBS had every opportunity to take him off the air, Mr. Stern said, citing several “delay buttons” and other mechanisms that the station installed over the years to buffer Mr. Stern’s often-profane radio act.

CBS yesterday declined to respond to Mr. Stern’s comments about the network and Messrs. Moonves and Hollander. The network is seeking significant damages from Mr. Stern and Sirius, including the $220 million stock payout and all of Sirius’s revenues from the more than 1 million new subscribers the station obtained after it announced its deal with Mr. Stern.