Nearly two-thirds of employers say they intend to make health care plan design changes to shift more costs to employees in 2011, according to a survey released Wednesday.

The Aon Consulting survey found that 65% of respondents plan to increase cost-sharing through actions such as boosting deductibles, copayments, coinsurance or out-of-pocket limits.

In addition, 57% said they expect to boost health care plan premiums paid by employees.

Those changes come amid major increases in health care plan costs. Just over one-third of respondents said their group health care costs rose at least 5% but less than 10% this year, while 18% said costs climbed at least 10% but less than 15%. Twenty-four percent, though, said cost increases were less than 5%, while 5% said cost increases were at least 15% but less than 20%.

The survey also details how expensive COBRA health care continuation coverage has become. For example, this year, the median monthly COBRA premium charged for single coverage in a preferred provider organization plan was $449, while the median monthly premium for family coverage was $1,310.

Through legislation passed in 2009 and later extended and expanded, the federal government pays 65% of the COBRA premium for employees who are involuntarily terminated. But that subsidy is available only to employees laid off through May 31. (BI, Aug. 23).

A total of 1,079 individuals participated in the survey, including 44% at employers with between 500 and 5,000 employees, 38% at employers with less than 500 employees and 18% at employers with more than 5,000 employees.

A summary of the “2010 Benefits Survey” and information on how to obtain the full survey is available at http://aon.mediaroom.com.