WellPoint Inc, the largest U. S. health insurer by membership, has canceled meeting with its investors that was scheduled for later this month, so that it can prepare for a congressional hearing on premium rate increases for individual policyholders in California.

To testify the planned premium increases of as much as 39% for many of Anthem's 800,000 individual policyholders in California, Angela F. Braly, Chief Executive of WellPoint Inc. has been called by a subcommittee of the House Committee on Energy and Commerce.

Trading on the New York Stock Exchange, WellPoint's shares slumped $1.37 to $57.96 in afternoon.

"What California families need is long-term health insurance security, so that they don't face sharply higher prices or fewer benefits", said Kathleen Sebelius, U. S. Health and Human Services Secretary.

WellPoint spokeswoman Kristin Binns said that the company looks forward to the average customer premium to increase roughly 24% to 25%.

"The company is confident that its rates were established consistent with actuarial principles and state law, and welcomes the opportunity to discuss the underlying rise in health costs and actuarial dynamics which resulted in the need to increase individual health insurance rates", said WellPoint in a statement.