By Huw Jones
BASEL, Switzerland, Oct 7 (Reuters) - European Union regulators are starting to investigate the rise of crossing networks inside big banks which draw share trading volumes away from exchanges, a senior supervisor said on Wednesday.
The Markets in Financial Instruments Directive (MiFID) has spawned new trading venues that are taking market share away from bourses, driving down tariffs and widening choice for users.
Bourses say they are at a disadvantage as the networks don't have to comply with MiFID's full set of transparency rules. Banks say volumes on crossing networks are small at about 4 percent of European share trading.
"We have been discussing this among the Euronext regulators. We are a bit worried about what's going on in the securities market," Hans Hoogervorst, chairman of Dutch markets regulator AFM told Reuters.
AFM and its equivalent in Paris, Brussels, Lisbon and London meet regularly to swap notes on pan-European exchange NYSE Euronext which they jointly supervise.
The EU next year will review a set of rules it introduced in November 2007 to boost competition in share trading.
"(With) MiFID it was intended there would be some fragmentation due to competition," Hoogervorst said.
"But that the fragmentation would get that big and relatively new crossing platforms would get so big was not expected.
"We feel it really merits close investigation of what's going on. The biggest danger would be that low impact trading would be going on the regulated markets and high impact trading -- with its price impact -- being done increasingly on opaque markets such as crossing networks.
"Is this in the interest of rational price discovery? Does not this make our monitoring of, for example, market abuse, extremely difficult?" Hoogervorst said.
The London Investment Banking Association said this week in a submission to the EU's executive European Commission ahead of the MiFID review that changes should be based on evidence.
"Broker dealers' crossing activities are part of a continuing process of improvement and automation of dealing to ensure that a firm is able to act in client's best interests and to ensure best execution of their orders," LIBA said.
Better reporting of prices after trades have been executed would alleviate regulatory concerns, the association added.
"Fundamental changes to the broad MiFID approach are thus not justified," LIBA said.
Hoogervorst said the Committee of European Securities Regulators, which groups national securities watchdogs such as AFM from all EU states has also begun looking at the issue.
Bourses say crossing networks should be classified as multilateral trading facilities under the MiFID rules and therefore, like exchanges, be required to flag prices before execution so rivals can offer a better price.
Tighter implementation of MiFID rules may be all that is needed rather than any changes to the law, Hoogervorst said.
"Suppose we come to the conclusion that these crossing networks are really multilateral trading facilities then they should be regulated as an MTF. Maybe we won't need different regulation but that existing regulation should be applied better," Hoogervorst said.
(Reporting by Huw Jones, editing by Jason Neely)