Oppenheimer Funds has become the lastest manager to admit losses from one of its investment vehicles, after blaming widening credit spreads for a fall in value of its municipal bond funds range, which accounts for almost $20bn (€14.8bn) of its assets under management.

The range of 10 vehicles, which includes the $8.6bn Rochester National Municipals and $11.2bn Rochester Fund Municipals vehicles as well as eight smaller state-specific funds, have seen significant falls in their net asset values over the last month.