FRANKFURT (Reuters) - Deutsche Boerse DB1Gn.DE and London Stock Exchange LSE.L expect their planned merger to cost more than 350 million euros ($375 million) in fees for bankers, lawyers, accountants and public relations, according to a regulatory filing made while doubts swirl about the 25 billion euro deal.

Carsten Kengeter, CEO of Deutsche Boerse talks to the media during the presentation of FinTec start-up facilities provided by Deutsche Boerse in Frankfurt, Germany, February 24, 2016. REUTERS/Kai Pfaffenbach

LSE is facing a bill of 175 million pounds ($216 million), while Deutsche Boerse will incur costs of about 150 million euros, plus taxes for each -- both figures above original estimates.

The two exchanges have also offered concessions to allay competition concerns about their planned merger, the European Commission said on Tuesday.

Although widely trailed by the exchanges, the pledge to spin off the French arm of clearing house LCH Clearnet is the first concrete offer to appease EU antitrust authorities. The groups had said last month they would sell the unit, LCH.Clearnet SA, to Euronext ENX.PA for 510 million euros.

Whether more follows will depend on how the European Commission, rivals and customers respond. However, the exchanges are positive that the remedies they offered will suffice, two people close to the deal said.

The European Commission has expressed antitrust concerns about the merger and the impact on the clearing of derivatives contracts in particular. The Commission has said it will decide whether to approve the deal by April 3.

The exchanges also need green light from German state of Hesse, which has called for the combined headquarters to be located in Frankfurt rather than London.

While regulatory approval is still pending, allegations concerning Deutsche Boerse Chief Executive Carsten Kengeter are also weighing on the future of the deal.

Deutsche Boerse said on Tuesday that its supervisory board backed Kengeter, who is the focus of an insider trading investigation for allegedly buying Deutsche Boerse stock in anticipation of a deal with LSE.

Deutsche Boerse stock had spiked once the merger plans became public.

German police and prosecutors have searched Kengeter’s office and apartment as they investigate whether secret merger talks with LSE were under way when Kengeter bought shares in his company in December 2015.

Deutsche Boerse’s supervisory board said it had no indication of wrongdoing on Kengeter’s part as talks with the London Stock Exchange had not yet started in 2015, adding the board unanimously expressed its full confidence in him.

German financial watchdog said on Tuesday that it has shared its finding on the investigation of Deutsche Boerse equities trades with the German prosecutor. ($1 = 0.9370 euros)

($1 = 0.9371 euros)