Dark pools operated by banks should improve pre and post-trade transparency and should operate under a more formal structure, the head of Europe’s umbrella group for securities regulators has said.

The comments, by Eddy Wymeersch, chairman of the Committee of European Securities Regulators, are the first by a top regulator since a spat has developed between the banks and some of Europe’s biggest exchanges over the bank’s “crossing networks”, a type of dark pool. Dark pools allow the matching of large blocks of shares without prices being revealed until after trades are completed.