Nearly three quarters of those seeking health insurance in the U.S. individual market in recent years faced roadblocks or were turned down due to prior medical conditions, a report released on Wednesday said.

The report by the Commonwealth Fund, a healthcare advocacy group, said 71 percent of an estimated 26 million people who tried to buy insurance on the individual market in the previous three years had problems purchasing affordable insurance.

About 35 percent said they were turned down or charged higher prices because of their medical history.

A majority of Americans obtain health coverage through their employers. The study by the Commonwealth Fund, which conducts research and advocates for healthcare reform, also said millions of people who lost jobs in the last two years during the economic slump joined the ranks of the uninsured.

About 52 million people living in the United States went without medical coverage for a period of time in 2010, the report said. That compares to 38 million people who went without healthcare coverage in 2001.

The report, which relied on data collected last year and in previous years, found that of some 43 million adults who lost jobs during the last two years, about nine million became uninsured. Others received coverage through a spouse or found coverage from another source, the report said.

Commonwealth Fund President Karen Davis said the report provides a benchmark to measure the effectiveness of the healthcare overhaul signed into law nearly a year ago by President Barack Obama.

"It tells a story of a continuing deterioration of healthcare accessibility, efficiency, safety and affordability over the past decade despite the fact that we spend more than any other country on healthcare," Davis said in a telephone conference with reporters.

Some provisions of the new law have gone into effect. But coverage requirements and new insurance exchanges for purchasing health plans do not go into effect until 2014.

The new law aims to provide health coverage for more than 30 million uninsured people. But Republicans say the coverage mandates discourage job creation and are trying to repeal it.

The law is also being challenged in the courts as unconstitutional. The challenges are working their way through the judicial system and the U.S. Supreme Court will likely end up deciding the matter.