Standard & Poor's has provided a rare insight into the quality of a buyout firm's debt after handing Blackstone Group a top rating. However, the ratings agency warned Blackstone, which today revealed a $94m (€76m) net loss for the first three months of the year, that an increase in leverage or poorly-performing investments could result in a downgrade.

S&P said yesterday it had assigned Blackstone a rating of A across its four buyout funds with an outlook of stable.