Starting this year, China will assign credit ratings to companies based on their environmental protection activities - the latest effort from the world's largest greenhouse gas emitter to tackle the country's pollution problem.

The rating will be a reference for authorities to provide such entities as banks and insurers to determine the new loan offerings and premium rates of pollution liabilities, respectively, to mainland companies, the ministry of environmental protection said January 2 in a statement.

The companies rated will be mainly from industries that cause heavy pollution or have overcapacity. They will be ranked on four levels -- green, blue, yellow and red -- with green being the best and red the worst.

In principle, the assessment will be done once a year, set before the end of April. Provincial environmental protection authorities can assign the ratings or make the evaluation via other social organizations, the statement adds.

The rules of the credit rating review will start effective from March 1.