The gloomier outlook for corporate debt in the US and Europe is turning a spotlight on another banking business that exploded during the credit boom, growing from next to nothing into a trillion-dollar industry in little more than four years.

Repackaging credit derivatives to create leveraged investments was a tiny business in the early years of this decade, but between late 2003 and the middle of last year analysts estimate that between $1,000bn and $1,500bn worth of these deals were sold.