After the alleged UBS trading error, exchange traded funds have become the new Marmite; cheap, opaque, and either loved or hated. The European Systemic Risk Board is the latest regulator to express concern over the risks of ETFs, and this time Ucits funds have been drawn into the gloop.

In an ESRB meeting on Wednesday, the regulator said it was "concerned" about Ucits exchange-traded funds. In a somewhat stately tone, the regulator said: "The ESRB is concerned about the opacity and complexity of these structures. Targeted disclosure and increased cooperation between securities market and banking sector supervisors are among a number of measures that might be taken to address these issues."