FRANKFURT (Reuters) - An unusually public boardroom dispute in Germany took a new turn on Monday, with the founder and major shareholder of a leading online broker telling Reuters why he wants to oust the company's chair and advocating for his candidate to replace him.

Bernd Foertsch, the publisher who controls nearly 20% of the German broker FlatexDegiro, informed Flatex on Friday that he would seek to oust the company's current chair, Martin Korbmacher, at a shareholder meeting in June.

"I would like to see a fresh start for FlatexDegiro - and he is not the right man for the job," Foertsch said on Monday in response to emailed questions from Reuters.

Flatex, which operates in 16 countries with 2.8 million customers, declined to comment. Korbmacher, who has previously declined to comment, didn't immediately respond to a request for comment.

It is the latest twist in an ongoing dispute after Foertsch successfully campaigned against the CEO, Frank Niehage, who resigned last month. On Friday, Foertsch also proposed two new board members, himself and a former UBS executive, Axel Hoerger.

Now, Foertsch is making clear in the emailed responses why he is backing Hoerger as the new board chairman.

"Axel Hoerger seems to me to be the right person to bring calm back to the company and to lead the supervisory board during what I consider to be the necessary restart," Foertsch said.

The back-and-forth has been remarkable in Germany, where a staid corporate culture makes it rare for such disagreements to occur in public rather than behind closed doors.

"The public debate was preceded by long discussions, but I found that these discussions did not result in any reactions, let alone changes," Foertsch said.

The kerfuffle began in March when Foertsch told a business magazine he would vote against Niehage and Korbmacher at the June shareholder meeting due to strategic mistakes, such as "sleeping through a cryptocurrency boom".

Niehage said he had resigned to avoid further damage to the company's reputation and to resolve tension with Foertsch.

In a departing swipe, Niehage accused Foertsch of trying to get a seat on the supervisory board "through the back door, claiming to know better what's good for the firm", and called on shareholders to vote in favour of Korbmacher at their meeting.

The broker, which was fined by its regulator in 2023 and told to fix serious shortcomings in its internal controls, has steadily increased its profits over the past year.

Last month, it posted a 340% increase in first quarter net profit from a year earlier, causing its shares to rally.

(Reporting by Tom Sims; editing by Jonathan Oatis)

By Tom Sims