US banks and auditors involved in the 2003 collapse of Parmalat will face legal action on a new front after more than 4,000 European shareholders in the defunct Italian dairy group announced they would seek damages in a class action suit in Italy.

The suit, to be launched soon in Milan, will accuse US and other financial institutions of contributing to the fraud that brought about Parmalat’s collapse amid €14bn ($21.7bn) of debt, alleging that they also took part in schemes aimed at defrauding Parmalat investors.