The Financial Conduct Authority, the UK market regulator, said it has found that almost a third of the mutual funds it looked at in a recent study were not providing "clear" information to investors – and added it had even found some evidence that suggested closet index-tracking.

The FCA first said it would look into whether mutual funds were "meeting investors' expectations" in March last year, before beginning its broader market study into asset management. It published the outcome of this earlier work on April 7.