By Maria Martinez and Valentina Za

BERLIN, June 9 (Reuters) - UniCredit said market take-up of its buyout offer for Commerzbank reached 10.9% on Tuesday, while the German bank said it had not been able to identify a single institutional investor that had tendered shares.

UniCredit and Commerzbank have traded barbs over the transparency of the take-up data, with Commerzbank saying tendered shares did not prove investors supported the bid, coming instead from banks which, in many cases, were also derivatives counterparties to UniCredit.

UniCredit has said the take-up highlights the positive market stance towards the bid.

The latest acceptance figures, which UniCredit published in a regulatory filing, lift the Italian bank's overall stake to 37.7%.

That stake rises further to 40.9% when including derivatives UniCredit holds that can be settled by delivering shares. UniCredit also holds cash-settled derivatives.

Both figures exceed the 30% threshold UniCredit set out to achieve with its offer and could hand UniCredit de facto control of Commerzbank.

A Commerzbank spokesperson said on Tuesday that information available to the bank showed no institutional investor had taken up UniCredit's €40 billion exchange offer, with retail investors' acceptance at 0.05%.

The Italian lender said Commerzbank leadership was fully entitled to recommend against UniCredit's takeover offer.

"However, it is not entitled to undermine the integrity of the offer process by making unsubstantiated allegations that UniCredit's statutory disclosures are misleading, artificially inflated or otherwise unduly interfering with the offer process," it said in a separate statement on Tuesday.

Commerzbank has been investigating the acceptance data and it has asked German regulator BaFin to do the same, saying it made no economic sense for investors to tender when the exchange offer's implied value was below market prices.

UniCredit said its disclosure complied with existing rules and could not be considered misleading.

"Any insinuation that UniCredit willfully conflated disclosure categories to artificially inflate perceived tender support for its takeover offer is without factual or legal foundation," it said.

UniCredit said in its filing that any other derivatives it held were to hedge downside risks on its Commerzbank position.

(Reporting by Valentina Za in Milan and Maria Martinez in Berlin; Additional reporting by John O'Donnell; Editing by Joe Bavier)

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