Whenever China's economy shows signs of faltering, Beijing typically moves to stimulate growth by boosting spending on infrastructure -- and that normally gives things a kickstart.

This time around, however, policy makers had resorted to the same strategy only to find themselves facing unusual headwinds, as evidenced by Tuesday's news that China posted its slowest growth in a quarter century in 2015.

Fixed-asset investment outside China's rural households, a closely watched indicator of construction activity, climbed 10.0% last year, the slowest annual growth pace since 1999 (investment rose merely 5.5% that year).

A recent state auditor's report on state-backed projects provides some clues as to why it is getting more and more difficult for Beijing to stabilize economic growth.

The nation’s top economic planner said last week that in 2015 alone it approved projects in sectors such as transportation, water and energy, with a total investment of more than 2.5 trillion yuan ($381 billion).

The National Audit Office checked on the progress of some of the large ongoing projects approved in recent years, involving 55 billion yuan of central government funds, the auditor said last week.

The auditor found that 88 infrastructure projects are behind schedule. In the railway sector, out of the 66 projects that gained the go-ahead from the government last year, 42 haven’t started construction, involving an annual investment of 10 billion yuan.

One of them is a new railway line linking Xuyong in China's western Sichuan province with Bijie in southwestern Guizhou province, which won Beijing’s approval in September. State-owned China Railway Corp. will cover about 10% of the initial 6.9 billion yuan in capital with the rest shared among the provincial governments of Sichuan, Guizhou and Yunnan. Another 6.9 billion yuan in investment comes from bank loans, the National Development and Reform Commission said in September.

The state auditor said in last week’s report that construction companies were unable to start their work because various investors in the project have failed to reach agreements on specific terms.

Apart from delayed projects, the auditor also found that several arms under the China Railway Corp. lied about their use of the funds given to them, saying over 1.2 billion yuan of funds claimed to have been invested were actually not used.

The auditor also named and shamed some cities, such as Shenyang in northeastern Liaoning province. It said that a 3.7 billion yuan railway line, planned to be finished by the end of March 2015, cannot be put into operation on time because the city government has failed to settle relocation compensation. The auditor report uncovered some idle funds and empty public housing projects.

The state auditor, which has been releasing follow-up reports on state projects each month since June, said it will hold those officials accountable for “nonfeasance, abuse of duties and slowness in taking action.”

Beijing’s anticorruption campaign has made local officials more careful in making use of public funds than before, some economists have said. Others blame weak domestic demand for slower investment. But not all agree.

“The demand is there (for investment). There are also many private investors sitting on millions of cash,” said Li Wenpu, a professor of economics at Xiamen University in east China's Fujian province.

What the government needs to do urgently is to break up the monopoly in state-dominated sectors to enhance investment efficiency, he said.

--Liyan Qi