Dark pools, a rapidly growing type of share trading facility, are to be reviewed by the European Commission amid signs that financial regulators are turning their attention to transparency in global equities markets.

The move comes on the heels of a warning last week by the US Securities and Exchange Commission over the transparency of dark pools, which allow the matching of large blocks of shares without prices being revealed until after trades are completed.

Mary Schapiro, SEC chairman, said she had asked the agency's staff to take “a serious look at what regulatory actions may be warranted in order to respond to the potential investor protection and market integrity concerns raised by dark pools”. Yesterday Ms Schapiro testified at a US senate banking committee hearing on over-the-counter-derivatives.