As head of audit regulator APAS, Ralf Bose was responsible for regulating EY, which audited Wirecard's accounts for years until the company collapsed following the discovery of a 1.9 billion euro ($2.3 billion) hole in its accounts.

"We will discuss the matter with the people involved," Economy Minister Peter Altmaier said on Friday, adding that he was "concerned" after learning overnight of Bose's share trading.

He pledged the matter would be "intensively" examined and said authorities would check if the rules had been followed.

Bose told a parliamentary committee on Thursday that he had dealt in Wirecard shares shortly before its collapse, according to attendees of the closed-door meeting. He said he bought shares on Apr. 28 and sold them on May 20.

There is no evidence that his trades broke any rules.

APAS declined to comment and said Bose was not available for comment.

Germany's financial regulator BaFin is looking into the matter, a spokeswoman said. It is not yet clear that an official investigation would be launched, she added.

The Wirecard case has become an embarrassment for officials and authorities, who have been accused of failing to sufficiently monitor the $28 billion company, which many had believed was a rare German digital champion.

Some politicians called for Bose to resign.

"Private share transactions with Wirecard shares just at the time when his own authority is investigating the company's auditor shows a huge lack of instinct," said Florian Toncar, a member of parliament. "APAS now needs a fresh start at the top."

($1 = 0.8252 euros)

(Reporting by Christian Kraemer, Patricia Uhlig, and Hans Seidenstuecker; writing by Thomas Escritt and Tom Sims; Editing by Simon Cameron-Moore and Pravin Char)