One of America’s most successful class action and securities lawyers, William Lerach, has agreed to plead guilty to conspiracy to obstruct justice while working at his former firm, Milberg Weiss, court papers said.

Mr. Lerach has agreed to serve one to two years in prison and to pay fines and forfeiture totaling $8 million, according to the court filings. He is admitting that he and others at Milberg Weiss made secret payments to investors in order to secure their participation as plaintiffs in securities lawsuits.

“I have always fought for my clients aggressively and vigorously in order to hold powerful corporations responsible when their actions harmed people, however, I regrettably crossed a line and pushed too far,” Mr. Lerach said in a written statement. “For my actions, I apologize and accept full responsibility for my conduct.”

Under the terms of the deal, the famed trial lawyer will not be required to testify against other targets of the investigation, a source said.

The agreement was filed this morning in federal court in Los Angeles. Mr. Lerach did not appear in court today and will be summoned to appear at a later date, a Justice Department statement said.

If Judge John Walter does not accept the recommended prison sentence, Mr. Lerach would be free to withdraw the plea and seek a jury trial.

Milberg Weiss and two of its name partners, David Bershad and Steven Schulman, were indicted in 2006 for aiding in a scheme to make undisclosed payments to investors who helped the firm file securities cases. Payments to the plaintiffs were often disguised as legal fees paid to outside lawyers, prosecutors said.

In July, Bershad pleaded guilty to a conspiracy charge and admitted in open court that the scheme operated in general terms as prosecutors asserted.

Last month, Mr. Lerach resigned from his latest firm, Lerach Coughlin Stoia Geller Rudman & Robbins. The plea deal guarantees no charges against that firm, sources said.