China's airport building boom over the past five years has caused a litany of graft and environmental problems, but has managed to boost local economies, the government's spending watchdog said.

Ten airport projects across the country cost taxpayers some 159 million yuan ($24.12 million) in false accounting and tax avoidance, while one northeastern airport cost double the amount it should have due to inflated contracts, the audit office said.

A total of 23 airports spent 1.94 billion yuan on projects that were not open to public tenders as they were supposed to have been, the audit office said, implying contracts were open to abuse.

"Relevant government departments are investigating further in accordance with the law and will ... find out who is responsible and hold them accountable," it said in a statement on its website ( www.audit.gov.cn ).

Other new airports were guilty of opening before final environmental impact studies had been completed, and some simply dumped their untreated waste water in nearby rivers and fields, the body added, saying this issue was now being addressed.

China has spent more than 68 billion yuan over the past five years building or expanding a total of 53 airports, and despite the problems encountered the process has been worth it, the watchdog said.

"Airport building has, to a definite degree, driven regional economic development and improved the local investment environment," it said, adding that subsidies to airports in remote areas boosted growth and created almost 60,000 jobs.

Air travel is developing rapidly in China amid a booming economy.

China has big plans for its airport network, especially in poorer and more remote regions in the far west, though many of these stylish new airports have struggled to attract customers and handle just a few flights a week, or none at all.

The country's massive infrastructure spending has provided officials with plenty of opportunity for graft.

Over the weekend state media announced the railways minister had been put under investigation for "serious disciplinary violations", which usually refers to corruption and abuses of power that can lead to criminal charges. (Reuters)