The two exchanges announced in February they were making a third attempt at a merger that would create a European trading powerhouse.

"We support it," Hohn was quoted as saying in Der Spiegel on Friday, adding that "management of the new group will be based more strongly on the Anglo-Saxon model".

In 2005, Hohn's TCI was a shareholder in Deutsche Boerse and was convinced the German exchange's stock would suffer if it bought its British rival.

His campaign was so intense that Deutsche Boerse's chief executive at the time, Werner Seifert, was forced out.

Hohn wrote to investors in the first quarter in a letter seen by Reuters that he believed shareholders stood to gain from the planned merger.

Separately, TCI is calling for rapid reforms at Volkswagen, having demanded this month that the carmaker - which is still battling a diesel emissions test-cheating scandal - overhaul its "excessive" executive pay scheme as part of a plan to boost profits and end years of "mismanagement".

"At VW we see an extreme form of the weaknesses of the German management model," Der Spiegel quoted Hohn as saying. "It leads to excessive bonuses motivating managers to give guarantees for jobs and pay wages that are too high."

(Reporting by Maria Sheahan; Additional reporting by Maiya Keidan in London)