China's economic slowdown is likely to contribute to weakening credit profiles for many of the country's major companies, according to an annual survey of the nation's top corporate issuers by Standard & Poor's Ratings Services.

S&P said that the top companies' balance-sheet leverage and profitability have deteriorated since 2008, as China's easy credit fueled an investment boom amid overcapacity in many industries.

"We believe the financial strength of the majority of corporates in our survey will weaken further in the next 12 months," said S&P credit analyst Christopher Lee.