Although China has declared war on haze, it needs at least 15 to 20 years to win the battle, a report said.

The China Annual Report on Low-carbon Economic Development 2014, released Thursday, focuses on China's smog last year, and it estimates that China may need 20 to 30 years to drive out smog completely, based on China's economic pattern and current technology level.

Xue Jun, main editor of the report and head of the Institute of Global Low-carbon Economy, said if the government adopts the toughest measure against smog and changes the economic pattern as soon as possible, it would still need 15 to 20 years.

It took developed countries such as Britain, Germany and Japan an average of 30 to 50 years to combat air pollution, the report said.

It also suggested levying a pollution tax on pollution sources, including carbon dioxide.

In addition to having a huge impact on the economy and people's health, Xue said, pollution "also threatens social security and China's reputation."

The institute is co-founded by the University of International Business and Economics and Japan's Nagoya University.

"China will wage war against smog and step up ecological protection measures by further saving energy and cutting emissions," said Premier Li Keqiang last month, at a meeting of the National Energy Commission.