For-profit insurance companies use a smaller amount of premium dollars on medical claims than consumers are being told, according to a Senate analysis of data filed with insurance regulators.

The analysis was released late on Monday by a top Democratic senator who has been pressing Cigna Corp and 14 other large health insurance companies for information about how much of premiums go toward medical care.

Senate Commerce, Science and Transportation Committee Chairman John Rockefeller, in a letter to Cigna, demanded that the company immediately clarify the amount of premiums it receives and the amount of the claims it pays for group health insurance products.

The data released in this letter reveals that while health care costs are spiraling upward, consumers are paying more and getting less, and the insurance industry doesn't want anyone to know what they are up to, Rockefeller said in a separate statement.

He wrote in the letter that: The analysis shows that in the individual and small group segments, insurers spend a significantly smaller portion of each premium dollar on patient care than they do in their large group businesses.

Instead of disclosing medical loss ratios (MLR) to help consumers and small business owners make informed health care choices, health insurance companies have hidden them behind a wall of corporate secrecy, the letter said.

According to the Senate analysis, the six largest public insurance companies' average ratio in 2009 was 74 percent for individuals; 80 percent for small companies with fewer than 50 employees, and 84 percent for large businesses.

America's Health Insurance Plans (AHIP), the industry association, disputed the finding.

Government data show that 87 cents of every premium dollar go directly to pay for medical care, AHIP spokesman Robert Zirkelbach said in an email statement.

The MLR is not an accurate measure of the efficiency or effectiveness of health plans. Administrative costs include programs and services that improve care and reduce overall health care costs for families and employers, Zirkelbach added.

Under healthcare legislation unveiled in the U.S. House of Representatives last week, insurance companies would be forced to give customers rebates if less than 85 percent of enrollees' fees is spent on actual health care.

In the letter to Cigna, Rockefeller also said the Senate Commerce committee's analysis found serious inconsistencies in the way Cigna and its subsidiaries provide business information to the public and to their regulators.

In August, the West Virginia Democrat asked Cigna for information about its handling of the small business group health insurance market and whether it dropped those whose employees made numerous and costly benefit claims.

Cigna spokesman Chris Curran said in response that the insurer complies with all regulatory requirements for the rates it charges and the terms of its insurance policies.

(Reporting by JoAnne Allen; Editing by Erica Billingham)