(Reuters) — Josef Ackermann, the former Deutsche Bank A.G. boss, resigned on Thursday as chairman of Zurich Insurance Group Ltd. over the apparent suicide of the Swiss insurer's chief financial officer.

Mr. Ackermann said the family of Pierre Wauthier, who had worked at Europe's No. 3 insurance group for 17 years, believed he shared some of the blame for his death.

"I have reasons to believe that the family is of the opinion that I should take my share of responsibility, as unfounded as any allegations might be," he said in a statement on Thursday.

"As a consequence, I see the possibility of a continued successful board leadership to the benefit of Zurich called into question," he said.

On Tuesday, police said Mr. Wauthier — who was found dead at his home in a lakefront suburb of Zug outside Zurich on Monday — appeared to have committed suicide.

His death came soon after the suicide of another top Swiss executive, the head of telecoms firm Swisscom in July.

A spokeswoman did not elaborate on what allegations Mr. Ackermann was referring to surrounding Mr. Wauthier, who was 53 and leaves a wife and two children.

Mr. Wauthier's death and the apparent suicide of Swisscom boss Carsten Schloter five weeks ago have prompted calls for greater support for boardroom high-fliers.

"Pierre was under a lot of pressure because there was a lot more pressure from above on the share price, this was an open secret," a former colleague, speaking on condition of anonymity, said. "Wauthier had effectively reached his career ambitions, CFO was his dream."

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Zurich's chief executive, Martin Senn, said he was not aware of any dispute that could have driven Mr. Wauthier to his death.

"We didn't spot any conflicts that could or should have led to such a death," Mr. Senn told Swiss TV.

Mr. Ackermann's departure means Zurich loses the leadership of a top European banker who transformed Deutsche Bank during a decade there and then played a role in the European financial crisis as chairman of the Institute of International Finance, the global banking industry's lobby group.

He was often touted as a possible candidate for top financial jobs in Switzerland, including as head of the Swiss National Bank, before he took the relatively low-key role at Zurich.

Mr. Ackermann has survived controversy before, having agreed in 2006 to make a €3.2 million payment, without any admission of wrongdoing, to avoid trial in a dispute over golden handshakes to executives at telecoms firm Mannesmann.

Since returning to Switzerland after leaving Deutsche in 2012, Mr. Ackermann has become a forceful advocate for the Swiss financial sector. He is one of few senior industry figures to keep his job through the financial crisis.

"Ackermann's mission when he came was to shake up Zurich, to infuse some a more dynamic mentality into it," said a person close to Mr. Ackermann.

"Yes, insurance isn't banking but there was still more 'oomph' to be wrung out of Zurich, he thought."

However, Mr. Ackermann's arrival at Zurich failed to steady the ship, since its top ranks have seen considerable change in the last 12 months.

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Former general insurance head Mario Greco left in mid-2012 to become head of Italian insurer Generali Group. Two weeks ago the head of its life insurance arm, Kevin Hogan, left to become American International Group Inc.'s head of consumer insurance.

"When the chairman leaves after you've already lost your head of global life, Mario Greco, and then the unexpected loss of Pierre Wauthier as CFO, it will lead to more uncertainty," Helvea analyst Daniel Bischof said.

Zurich's vice chairman, Tom de Swaan, will take over as acting chairman. A former ABN Amro banker who has been on the board of Zurich since 2006 and vice chairman since March 2012, he also served as acting chairman before Mr. Ackermann's arrival last year.

On Aug. 15, Zurich said it would be hard-pressed to meet certain performance targets after posting a 27% fall in second-quarter net profit due to natural disaster payouts, which topped those of European rivals because of its high exposure to the United States.