Senator Dianne Feinstein, Democrat of California, sharply criticized Anthem Blue Cross of California on Tuesday over its plans to raise health insurance premiums by as much as 39 percent, and she said that the move provided a vivid example of why major health care legislation is needed.

“It is unconscionable that Anthem Blue Cross would consider increasing health insurance premiums for Californians by as much as 39 percent, especially at a time when so many people are experiencing economic hardship,” Ms. Feinstein said in a statement. “I can think of no better example of why we need health insurance reform, and this kind of behavior is a stark reminder of why any reform plan should establish a rate authority to keep insurance rates affordable.”

Ms. Feinstein also called on Congress to repeal the limited exemption from federal antitrust laws that insurance companies have enjoyed since 1945. The House was supposed to vote this week on a standalone measure to repeal the exemption, but all votes were delayed because of weather conditions in Washington. The Senate did not include provisions to repeal the antitrust exemption in its health care bill.

Separately, Senator Barbara Boxer, Democrat of California, wrote to the California attorney general, Edmund G. Brown Jr., urging him to investigate Anthem’s proposed rate increases.

“California families are struggling to hang onto their health insurance through this economic downturn, and I ask that you investigate the rate increases proposed by Anthem Blue Cross to determine whether or not the company has broken state law,” Mrs. Boxer wrote. “Anthem Blue Cross has a responsibility to provide a detailed justification for these rate increases to the citizens of California. Our constituents have a right to know that they are getting value for their money.”

In her statement, Ms. Feinstein said she had urged state lawmakers in California to consider legislation that would empower the California Insurance Commissioner to regulate insurance rates. Kathleen Sebelius, the secretary of health and human services, has also demanded that Anthem explain its rate increases, lending federal muscle to an issue normally addressed by state authorities.

The rate increase in California could serve to galvanize Congressional Democrats in Washington who have been struggling to get their big health care legislation back on track. President Obama has announced plans to convene a bipartisan summit on health care on Feb. 25, but Democrats still do not see a clear road map to securing the votes needed to advance the legislation, particularly in the Senate, where the Republicans now control 41 seats — a sufficient number to filibuster the health care bill.

Ms. Feinstein said that there were few choices for people seeking to buy health insurance in Los Angeles. “Two insurance companies controlled 62 percent of the health insurance market in Los Angeles in 2008, leaving people with few alternatives when these companies impose dramatic rate increases,” she said.

She added: “The state must move aggressively to protect Californians from unfair premium hikes.”

Copyright 2010 The New York Times Company