China's hidden local government debt has swelled to more than half the size of the economy, according to economists at Goldman Sachs Group Inc., who said the government will need to be flexible in dealing with this as revenue is already under pressure due to a slowdown in land sales.

The total debt of local government financing vehicles rose to about 53 trillion yuan ($8.2 trillion) at the end of last year from 16 trillion yuan in 2013, the economists wrote in a report. That's equal to about 52% of gross domestic product and is larger than amount of official outstanding government debt.

The LGFVs are a tool for governments to borrow money without it appearing on their balance sheets, but it is seen as the same as a government liability by financial markets.