Pimco and a group of hedge funds have begun court action against Spanish regulators over their wind-up of the failed banking group Banco Popular — including a bid to get hold of a Deloitte valuation at the heart of the saga.

The bondholders launched legal proceedings in the national Spanish court in Madrid on Wednesday evening to challenge the actions of the country's Fund for Orderly Bank Restructuring, or Frob, in enacting the sale of Popular to Santander on June 7. The Frob is the mechanism by which the Spanish government can rescue banks in crisis.