The European Commission on Wednesday formally put an end to the proposed merger between Deutsche Boerse AG and the London Stock Exchange (LSE.

“The commission’s investigation concluded the merger would have created a de facto monopoly in the markets for clearing fixed income instruments,” the commission says in a statement.

Specifically, the commission was concerned that the merger would have created a monopoly by combining Deutsche’s clearing house, Eurex, with the LSE’s clearing houses in the U.K., France and Italy, which would also impact markets for settlement, custody and collateral management.

“The merger between Deutsche Boerse and the London Stock Exchange would have significantly reduced competition by creating a de facto monopoly in the crucial area of clearing of fixed income instruments. As the parties failed to offer the remedies required to address our competition concerns, the commission has decided to prohibit the merger,” says Margrethe Vestager, commissioner in charge of competition policy, in a statement.

The exchanges proposed to address the competition concerns by selling off the LSE’s clearing house in France. However, the commission ruled that while this would resolve its concerns relating to single stock equity derivatives, it wouldn’t address concerns about fixed income clearing.

Both firms expressed disappointment with the ruling. “The prohibition is a setback for Europe, the Capital Markets Union and the bridge between continental Europe and Great Britain. A rare opportunity to create a global market infrastructure provider based in Europe and to strengthen the global competitiveness of Europe’s financial markets has been missed,” says Joachim Faber, chairman of the supervisory board of Deutsche Boerse, in a statement.