LANSING, MI - Some Michigan insurance companies are charging women significantly higher rates than men, according to a new report from the Coalition Protecting Auto No-Fault.

The study was conducted by independent insurance expert Doug Heller, whose earlier work for CPAN found that blue collar Michiganders were paying more for auto insurance.

Heller completed the survey by collecting nearly 100 online premium quotes from the websites of insurance companies. To get the quotes, he kept factors such as the address, type of car and annual miles constant, and tested drivers with perfect driving records. He tested rates in Detroit and Brighton.

The survey identified three companies that charged the tested women more based on their sex or marital status.

Progressive, Esurance and Liberty Mutual raised premiums for widows and other single women between 5 and 10 percent as compared to married women, Heller found in the study.

For men and women with perfect driving records, the same vehicle and the same address, Progressive charged women as much as 38 percent more, according to the study. Esurance, meanwhile, charged women 33 percent more than men with the same record, vehicle and address, the study found.

CPAN alleges the actions of these insurance companies are illegal, citing a portion of law that states "An insurer shall not establish or maintain rates or rating classifications for automobile insurance based on sex or marital status."

Esurance, Liberty Mutual and Progressive did not immediately respond to a request for comment.

Insurers can use other factors to set rates, the law states, including the age of the driver, daily or weekly commuting mileage, vehicle characteristics and number of household members with licenses.

"Women already struggle for equal pay, and here we have insurance companies piling on by charging women drivers more for auto insurance. It is a blatant violation of the law and must be stopped," said State Representative Sherry Gay-Dagnogo, D-Detroit, who serves on the House Insurance Committee, in a statement.

The study found that widowed women pay more than those with living husbands through those three insurers, while men whose spouse died actually saw rates from Progressive and Esurance drop. Liberty mutual, meanwhile, raised rates 5 percent on all individuals who lost a spouse.

The Insurance Alliance of Michigan, an association representing insurance companies and advocating for legislative changes to Michigan's no-fault auto insurance, said the CPAN study distracted from the real issue.

"Again, medical providers and trial lawyers want to distract from the real problem in Michigan's costly auto insurance system, rampant fraud, medical treatment overcharging and an unlimited, lifetime medical benefit mandate," said Dyck Van Koevering, general counsel for the Insurance Alliance of Michigan.

"The insurance industry chooses to focus on those factors that really drive up the cost of auto insurance for everyone and invite the Coalition Protecting Auto No-Fault to join us to work on real solutions that benefit Michigan drivers."

Lawmakers are looking to make changes to the state's no-fault system this year.

Heller, meanwhile, pointed to the rate setting as one reason rates were so high.

"When insurance companies are allowed to slice, dice, and price Michiganders according to personal characteristics that have nothing to do with their driving, many good drivers end up paying more than they should or driving uninsured, and it's one of the reasons premiums are so high in Michigan," Heller said.