An economic slowdown and extremely tight credit conditions pushed corporate debt to a record high in China last year, according to experts.

Defaults for Chinese corporate bonds — issued in both U.S. dollars and the Chinese yuan — soared last year, according to numbers from two banks.

Yuan-denominated debt rose to an "unprecedented" 119.6 billion yuan ($17.8 billion) — four times more than 2017, according to a February report by Singapore bank DBS.

Japanese bank Nomura's estimates were even higher, putting the size of defaults in onshore bonds — or yuan-denominated bonds — at 159.6 billion yuan ($23.8 billion) last year. That number is roughly four times more than its 2017 estimate.

Offshore corporate dollar bonds, or U.S. dollar-denominated debt issued by Chinese companies, followed the same trend. Nomura said the amount of such debt rose to $7 billion in 2018, from none the year before.