The national environmental watchdog has cut links to more than 70 agencies that provide environmental impact assessments, a move to rein in the corrupt trading of power and money.

In February, corruption related to environmental impact assessments was exposed in the Ministry of Environmental Protection, the inspection team from the country's top anti-corruption authority said.

For example, some leaders and their relatives traded power for money by helping companies get approval or by opening their own agencies to take advantage of their relationship with the ministry.

The provincial and city-level environmental protection bureaus also have similar corruption problems involving environmental impact services, the team said.

Minister of Environmental Protection Chen Jining required the ministry's eight affiliated agencies to become independent commercial companies, and the provincial and city-level environmental watchdogs were ordered to cut links with their affiliated agencies.

Chen said that it is not acceptable for officials in the system to make money from environmental impact assessments, adding that the ministry will tighten its management of these services to reduce corruption and the pollution emitted by the projects.

The ministry has punished around 140 agencies due to practices like hiring "ghost" employees - engineers who do not work at the agency but lend the agencies their certificates.

The ministry has also tightened the management of environmental impact assessments, which are considered the first step to control pollution from projects, the ministry said on Tuesday.

In 2015, the ministry approved 159 projects with a total investment of 1.57 trillion yuan ($235 billion), down from 237 projects in 2014.

In addition, the ministry rejected 21 projects partly because of their potential to pollute the environment.

For example, in March it rejected Xiaonanhai Dam, one of China's biggest hydropower dam projects, because of the potential negative influence on the environment.

The dam is located in the upper reaches of the Yangtze River.