The UK's Competition Commission said today that a bid for the London Stock Exchange by Deutsche Börse or Euronext would hurt competition in the UK markets and suggested they cede control of their clearing divisions if they wanted offers to succeed.

Issuing its preliminary findings on both takeovers, the authority said that retaining the clearing services would give the exchanges "the ability and incentive" to make it difficult for competitors to access the clearing agencies, and hamper efforts to compete with the LSE.