The British exchange made the announcement late on Wednesday, hours after the European Commission formally blocked the deal with its German rival. The Commission said the deal would have resulted in a monopoly in the processing of bond trades.

LSE said in February it would face costs of around 175 million pounds for the deal and it will still have to pay a significant portion of that despite the merger not going ahead.

The buyback will happen in two tranches, with the first beginning on Thursday and consisting of up to 100 million pounds of shares.

Barclays and RBC will be managing the buyback.

($1 = 0.8041 pounds)

(Reporting by Rachel Armstrong, Editing by Lawrence White)