Standard & Poor's has warned investors of the risk of rushing into speculative-grade assets, as covenant-lite structures make up the majority of new leveraged loans.

According to the head of global credit products capital markets at one bank, 15 out of 18 leveraged loans in the market this week were so-called "covenant-lite" loans with weaker protection for investors. Most of the deals in the bank's pipeline also boast weaker default triggers as investors push for higher yields.