LSE, like other European exchanges, has been losing market share to upstart multilateral trading facilities (MTFs) such as Chi-X and BATS since pan-European regulation opened the market to competition in 2007.
"Market conditions are expected to remain testing in the current quarter," said LSE Chief Executive Xavier Rolet in a statement.
"We continue to work on ways to leverage the assets and develop opportunities across the group to provide a platform for growth further ahead."
Revenue fell to £154.9m for the three months to end-December.
That included a drop of 13 per cent in post-trade revenues due to an expected decline in interest on the margin held in its clearing business from high levels a year ago, it said.
Its information and technology services rose 3 per cent, with a first-time contribution from newly acquired firm MilllenniumIT, LSE said.