Speculation surrounding a takeover of London Stock Exchange by its Frankfurt rival Deutsche Börse is being viewed skeptically by European stock market regulators. The Committee of European Securities Regulators are concerned that a possible takeover would make regulation in the sector more difficult. "The more cross-border stock exchange mergers there are, the more difficult it will be for regulators to control them with current means," CESR General Secretary Fabrice Demarigny told the business daily Handelsblatt in an interview. CESR, set up in 2001 by the European Commission, is a body whose members are stock market regulators from all EU countries. Demarigny said that should it come to a single European market, then it would require a single regulator. Deutsche Börse is competing with archrival Euronext to take over the LSE. The shareholders of Deutsche Börse have had mixed reactions to the plans so far.